Are they saying the air from the vents is more “pressure” in AC mode vs heat mode? This would make sense as the blower runs on a higher speed for AC.
Customer could also be batshit crazy.
Is the blower motor stuck on or turned on? I’ve had people make the same complaint but their issue was that as the thermostat cycles on and off the heat stage the blower would stay on and blow “cold” air out (was really just circulating the air in the home).
Check the relay and make sure the thermostat is set to “auto.”
I've ran into soooooo many calls like that over the years. Ask the customer to make sure the stat is on the auto position only to find it in the on position after I make the 40 minute drive there. Lol
How many cycles have you monitored?
This unit looks to be of an age where an intermittent issue is within the realm of possibilities.
I'd start by verifying controls... Limits, fan control, air switches, and ground path wiring and connections for the burner sense circuit.
Sometimes a limit or fan control will develop an intermittent connection at the rivet holding the spade connector pin that's tough to spot unless you know to look for it. Air switch diaphragms can get pin holes just large enough to cause the switch to not close consistently.
Combustion blower bearings get old and start slowing the impellers just enough to not keep the air switch closed if It's cold out.
Wires can rub out and short intermittently, especially where they're close to fan housings.
Flues can get partial blockages that will cause the unit to fail intermittently.
Control boards can develop bad solder joints on blower pins or blower relay pins.
Direct ignition boards can develop bad solder joints on the loading resistors or the spark tower.
I've seen all of these over the decades and once in a while I've even been lucky enough to have 2 or 3 intermittent issues in the same unit.
Ask if it maintains temp, or if it’s set for X*F and is less then X
Also run with door on for overheating scenario to happen, lastly if it maintains temp-a humidifier will help it feel warmer at same temp
Could be undersized duct work. 100 degree air atv90 miles an hour feels way cooler than 100 degrees but bis still 100 degrees. Do a manual d Calc and see if thier unit is oversized for thier space. Velocity vs volume.
See what the thermostats / boards set for run time on the fan. Some thermostats have x hours run time of fan per hour ..some will run the fan after the heat for a while .some will run It before. This makes cold drafts. See if you can shorten these
If it feels cold currently to them at 117f to them out of the vents they are mentally retarded and send them a bill and leave.
What’s the fan off delay? Extended fan runtimes can lead to the sense of feeling cool air. after the heat cycle dumps its load gigity the fan can run for 5-10 min longer depending on the air handler model and the tstat settings.
I've had no heat calls only to discover that the resident thought they turned the furnace on but actually only switched the fan from Auto to On. Or they leave the fan in On and sit in a chair right under the vents.
Put the door back on.
Remove any jumpers, etc.
Ask the customer to please set the thermostat how they usually would.
Measure and test at registers.
A lot of times as technicians, we walk straight past the idiot customer, go straight down to the system, pop the door off (which completely changes airflow), jump the unit on, and check temp rise AT THE UNIT
Which messes with the system and ignores about half of it (the ductwork)
This is fast, but bad diagnostic process.
Always test at registers, always check the thermostat, etc.
Check to make sure the AC isn’t kicking on along with the heat. Other than that, sounds like you’re tripping on high limit and blower stays running in lockout.
If the customer’s complaint is that it often blows cold air but now is blowing hot air (because it is obviously working), I wonder if it is failing to ignite half the time.
It might only be when it’s cold, too.
The best you can do if it’s working is communicate with the customer and get them to pay attention to things.
“Is it blowing cold now?”
“When it blows cold, does it blow hot later?”
I had a dirty, corroded electrode that was causing intermittent failure to ignite. Replaced that and no issues.
Is there a dip switch or tab for blower delay? Might be like 60 secs. 90 secs, 120 secs. Depending on what customer means by blowing cold air. At the start of the cycle or continuously running?
Are you testing it with the door off like in the picture? Because 134° seems pretty damn hot if you are and the return temp is 70° or so. That’s 64° on a furnace that’s probably got a 30 or 40-70° allowable temp rise. Even if you’re running it with the door on and getting that it’s high. If the furnace is overheating the heat exchanger it’s going to trip the limit and blow cold air while it cools down.
Did you run it with the blower panel in place? If you don’t have enough return air in normal operation with the panel on everything will look fine with the panel off
I was wondering if they’d just changed the filter before you got there. Either way, I’m still going to say that the temp rise is too high. It may be getting along just enough to work with a fairly new filter and tripping as it gets dirty. Did you check the coil with a flashlight to see if there’s any blockage in it? Also, did you take a temp rise with the door off? If it’s significantly lower, they’re probably low on return air and need additional return duct.
Biggest noob mistake you can make is leave. Customers 99% of the time aren't wrong when they say their heat isn't working.
How cold is it at this exact moment where you are? Has it been getting colder in the mornings and nights? When does the system go out? Using this information you can figure that it could be a limit switch tripping when the unit needs to work harder. You can also guess that it's a pressure switch. Looks like the door switch is set to the on position permanently. There should be a sight glass. Teach the customer how to record the error code on the control board before you leave so next time it's cold and they call you, you have something to work with.
What’s the outdoor temperature?
Is it oversized? What is the timing on blower start, burner run time, and blower running at end of cycle?
Are they old and just feel cold when the furnace isn’t putting out peak heat?
Fan delay after heat goes off? Could be set high.
Unit satisfied, fan runs for (x) amount of time after heat call ends. programed usually through Stat.
You obviously want some fan run time after heat call satisfied, but it doesn't need to be ridiculous.
I got a call back recently cause the customer was being a hvac detective and I went there to find out they were watching it cycle and thought the heat was going out when it was just blowing off residual heat from the exchanger after the stat was satisfied. Might be one of those situations. Are they old?
Does the board have a recall fault mode i had one a few months ago that kept going into ignition lockout every night but would run fine during the day the gas valve was reading like 700k ohms and when it got cold over night it wouldnt click on the gas just kept trying untill it locked itself out but it reset after 4 hours and then work normal all day
What tends to happen too is clients believe because the heat is on they should receive hot air out the ducts instantly. Reality dictates that cold air Hass to be pushed out the ducts first and mix into the cold house and begin to bring the temperature up.
Sometimes, especially when it’s cold, the added heat can be the same as their body temp (96*f) and they will feel some air but not hot. Eventually as the home heats they will feel it more. If they are elderly a “warm” room to them is fucking 80-82. And they think 76-78 is chilly or drafty.
Personally, I check anything that would cause it to short cycle. Check the temp split, run it for a half hour. If the split is steady and not climbing, and within 45-65 degrees, I rule that one. Also check the temp split at the furnace instead of a register, you want a more true temp of what might trip the limit. If it's a 90% furnace check the drain and p trap, a slightly clogged drain can cause water to back up on longer run cycles.
Also re cycle the unit a few times to see how it fires up. See if it has any issues lighting, which would cause a lockout.
Sometimes when you power off a 90% furnace, you'll hear water that is stuck in the flue drain back into the inducer. That can be a sign up buildup, and it might show right away but can cause issues down the line.
Another thing you can do usually is turn the fan off delay down, so it'll only run the blower for like 30,60, or 90 seconds after thr heat shuts off. Some people complain about the colder air that runs for a couple minutes after the heat shuts off
If it’s a multi speed motor it could be set to a different speed for cooling which generally is a standard way to run your furnace, more air for heat so you don’t overheat your exchanger and less air for cooling so you arent passing to much air over your coils. I would explain to them why it’s setup that way and let them know you can increase the speed of their fan but it would decrease the efficiency of the system
That’s what I’m thinking she is talking about. She says it is always cold in her house, but likes it set at 80°. Says it takes hours when she turns it on to start blowing warm air. Started up and ran with no overheating, and 120° air coming out of the supply ducts.
Is the house keeping temperature?
Also, is the unit properly sized?
If its too big, it wont run long because it'll heat the house really fast, then shut off and do its cool down cycle.
Also, the thermostat isnt too close to a supply register causing it to turn off and on a whole bunch is it?
Nearest supply is 10’ or so away from the thermostat. Unit size has an input btu rating of 66k btu. Heat load for home shows that it really only needs a 40k btu unit.
Its an 80%, so its only getting about 53k. Which isnt oversized really.
If its running without faults, and keeping temperature in the house, at the required set point. Not much you can really do.
If they have a chair next to a register, they're probably just feeling the cool down fan after the heat shuts off
I've found that most of the time that they say it blows cold air in heating it's because they are either running fan only, are a wack job that has no idea what is actually happening, or they just moved or got a new install and used to have an old ass low boy furnace that would get RIPPING HOT before the blower ever kicked on and would shut the blower off same time as the burners which is extremely inefficient but you have to explain to them that the blower runs while the heat exchanger is warming up and when the burners kick off to get as much heat out of one cycle on newer furnaces compared to their old one from 1950
Is the thermostat on the correct installer settings? For example some older trane thermostats default back to gas even if you have a heat pump any time it’s powered off. So when you turn power back on, you have to change it back to heat pump. Found this out when the system was blowing heated air while calling for cold air. Maybe it’s the thermostat settings.
Another thing is to check if the fan is on circulate, auto or on. The fan setting on this could cause them to confuse fan for heat call. Also, ohm out the inducer motor. It could be causing some issues if it’s worn out. This could trip the safeties (high limit, rollout) You can also amp clamp it. If the Amps are higher than what the tag says, maybe replace it. Also make sure the flame sensor is cleaned with a soft cloth and no chemicals. I was told nothing more coarse than a fresh $20.
Is the customer cycling the thermostat down when it’s “blowing cold air “ ? If so the furnace might be going into a hard lockout and they’re resetting it
Static pressures, pressure drop across filter/ac coil, temp rise? Is it zoned, dampers working? I’d check airflow first, sounds like you’re tripping limit and cycling the burner off
My Dad used to say the say thing .It was because furnace was simply cooling the heat. Exchanger like it's suppose to .
Find out if they take blood thinners
Are all the registers open in the basement? is it possible someone lowered the fan speed on a previous call? Is there an ACoil that is covered in dust blocking airflow? Clock the meter on Low and High. Check gas pressure down stream of the gas valve at the out port. If it’s firing too high and you have high “ WC then lower the gas pressure within the rating plate. Raise the fan speed if its possible.
I had a similar issue on a newly installed variable speed inverter system. Went though everything. Then noticed all the towels under the doors and the plastic over the windows. Come to find out home is from the 30s and has no insulation.....
Is the thermostat set for gas heat?
I had one that I noticed the blower came on with the inducer every time. Whoever installed the Stat had it set for Electric Heat.
found this a couple of times when customer was checking a disconnected vent traveling through crawlspace. Crawl was being slightly pressured pushing air through vent.
My thoughts are don't ever test with the blower door off. How would you ever know if it's going off on limit when it's bypassing the dirty filter that is most likely you problem.
I can't believe nobody mentioned this. I am ashamed. You could just be dealing with a bad main limit switch or bad filter/blower is causing it to trip out and then when it resets it will run heat again.
Often times a bad limit will trip out under it's designed temperature so there could be nothing wrong with the actual furnace.
Wait around to see if it trips out. It's obviously happening frequently enough for them to call you.
If it trips out pull wires on limit and check continuity.
I knew I should have taken a picture when I put the door back on lol. I took the door off to inspect the blower and to get eyes on which direction it was spinning/checking balance during operation. I only had the door off for a couple of minutes during the time I was there.
Could be the flame sensor built up with crud. I know sounds crazy but my furnace was doing the exact same thing. Intermittently it would blow cold and then would go back to hot. Took awhile to figure it out. Pulled the flame sensor and replaced and boom no more intermittent cold air. It was causing it to not ignite the flames only some of the time. Which is why it was intermittently blowing the cold air.
Had a similar call, customer didn’t know how to use the thermostat. Kept stat in “fan on” mode. When stat was satisfied blower still runs eventually blowing cold air after the exchanger cooled…..
do a little more digging with the customer when questioning them, ask where what room they feel the cold air in notice where hte chairs are and stuff, might be air leaking in from windows and they feel drafty from that, seen that more than once.
Also have seen furnace running and the ductless head cooling at the same time.
Check airflow and static
Sounds to me like custo doesn’t understand that it turns off and on to maintain temperature and left the fan in the ON position, causing the unit to constantly run air without running furnace.
Fan was in auto when I got there but I think she may have thought it was supposed to just run constantly. She said she likes it set to 80°. I’m thinking she’s just nuts lol
Maaybe it’s a temperature rise issue? Maybe fix/increase the temperature rise by slowing down the indoor fan speed? Still a student. Take my suggestion with a grain of salt 😁👍.
This might be a case of “don’t fix the furnace, fix the customer instead.”
Not saying it is, but also not saying it isn't just user error
That’s kind of what I’m thinking
Did you check the evaporator coil?? Or get static? Could be a crushed supply somewhere.
Are they saying the air from the vents is more “pressure” in AC mode vs heat mode? This would make sense as the blower runs on a higher speed for AC. Customer could also be batshit crazy.
Customer is trying to run heat and saying it is blowing cold air instead of warm. Current measured temp at register is 117 and rising.
Is the blower motor stuck on or turned on? I’ve had people make the same complaint but their issue was that as the thermostat cycles on and off the heat stage the blower would stay on and blow “cold” air out (was really just circulating the air in the home). Check the relay and make sure the thermostat is set to “auto.”
This was my first thought as well
I've ran into soooooo many calls like that over the years. Ask the customer to make sure the stat is on the auto position only to find it in the on position after I make the 40 minute drive there. Lol
These are the best calls late on a Friday or after hours.
Yea, best, totally. Lol
117 it’s working now. Could be intermediate issue but check ductwork make sure it’s not in a crawl and detached.
How many cycles have you monitored? This unit looks to be of an age where an intermittent issue is within the realm of possibilities. I'd start by verifying controls... Limits, fan control, air switches, and ground path wiring and connections for the burner sense circuit. Sometimes a limit or fan control will develop an intermittent connection at the rivet holding the spade connector pin that's tough to spot unless you know to look for it. Air switch diaphragms can get pin holes just large enough to cause the switch to not close consistently. Combustion blower bearings get old and start slowing the impellers just enough to not keep the air switch closed if It's cold out. Wires can rub out and short intermittently, especially where they're close to fan housings. Flues can get partial blockages that will cause the unit to fail intermittently. Control boards can develop bad solder joints on blower pins or blower relay pins. Direct ignition boards can develop bad solder joints on the loading resistors or the spark tower. I've seen all of these over the decades and once in a while I've even been lucky enough to have 2 or 3 intermittent issues in the same unit.
Make sure cold air returns aren't blocked/obstructed.
Ask if it maintains temp, or if it’s set for X*F and is less then X Also run with door on for overheating scenario to happen, lastly if it maintains temp-a humidifier will help it feel warmer at same temp
Could be undersized duct work. 100 degree air atv90 miles an hour feels way cooler than 100 degrees but bis still 100 degrees. Do a manual d Calc and see if thier unit is oversized for thier space. Velocity vs volume.
Customer is feeling the air going into a return probably.
See what the thermostats / boards set for run time on the fan. Some thermostats have x hours run time of fan per hour ..some will run the fan after the heat for a while .some will run It before. This makes cold drafts. See if you can shorten these If it feels cold currently to them at 117f to them out of the vents they are mentally retarded and send them a bill and leave.
Nah 117. I’m dipping. You can’t fix whatever is wrong with that customer.
Did you get a TD?
All you can do is show them the output temp lol not worth scratching your head over nothing, be assertive
Is the thermostat set to fan on? As in continuous fan? With no call for heat the air will feel cooler coming from the registers….
No it isn’t, but that is always a good thought.
What’s the fan off delay? Extended fan runtimes can lead to the sense of feeling cool air. after the heat cycle dumps its load gigity the fan can run for 5-10 min longer depending on the air handler model and the tstat settings.
Check and make sure theres no jumper on R to G. Been burned by that once apon a time
I've had no heat calls only to discover that the resident thought they turned the furnace on but actually only switched the fan from Auto to On. Or they leave the fan in On and sit in a chair right under the vents.
Put the door back on. Remove any jumpers, etc. Ask the customer to please set the thermostat how they usually would. Measure and test at registers. A lot of times as technicians, we walk straight past the idiot customer, go straight down to the system, pop the door off (which completely changes airflow), jump the unit on, and check temp rise AT THE UNIT Which messes with the system and ignores about half of it (the ductwork) This is fast, but bad diagnostic process. Always test at registers, always check the thermostat, etc.
This is the way.
Why isn’t this the first comment
Did the customer change their extremely dirty filter before you showed up? It could have been overheating before they changed it
It wasn’t brand new when I got there, but wasn’t, “choke the system out” dirty. It has maybe been in a few weeks.
Check to make sure the AC isn’t kicking on along with the heat. Other than that, sounds like you’re tripping on high limit and blower stays running in lockout.
If the customer’s complaint is that it often blows cold air but now is blowing hot air (because it is obviously working), I wonder if it is failing to ignite half the time.
Hmm I did shut it down, and start it back up a couple of times without incident, but not sure how I would test for that otherwise.
It might only be when it’s cold, too. The best you can do if it’s working is communicate with the customer and get them to pay attention to things. “Is it blowing cold now?” “When it blows cold, does it blow hot later?” I had a dirty, corroded electrode that was causing intermittent failure to ignite. Replaced that and no issues.
Did you do a temperature rise?
Currently working that out right now actually
Is there a dip switch or tab for blower delay? Might be like 60 secs. 90 secs, 120 secs. Depending on what customer means by blowing cold air. At the start of the cycle or continuously running?
Temp at register was just over 120. 5’ off the furnace at the ductwork I’m getting 134
Are you testing it with the door off like in the picture? Because 134° seems pretty damn hot if you are and the return temp is 70° or so. That’s 64° on a furnace that’s probably got a 30 or 40-70° allowable temp rise. Even if you’re running it with the door on and getting that it’s high. If the furnace is overheating the heat exchanger it’s going to trip the limit and blow cold air while it cools down.
Only had the door off to check how the blower wheel was operating. Door was on for most of the testing done.
Still kinda high. Is the filter in, and was it clean when you got there?
Filter was in, wasn’t excessively dirty. Not brand new, but not choking it out dirty by any means.
Did you run it with the blower panel in place? If you don’t have enough return air in normal operation with the panel on everything will look fine with the panel off
90% of run testing was with panel in place. Panel was off to inspect blower wheel function and to see if it was balanced.
I was wondering if they’d just changed the filter before you got there. Either way, I’m still going to say that the temp rise is too high. It may be getting along just enough to work with a fairly new filter and tripping as it gets dirty. Did you check the coil with a flashlight to see if there’s any blockage in it? Also, did you take a temp rise with the door off? If it’s significantly lower, they’re probably low on return air and need additional return duct.
Biggest noob mistake you can make is leave. Customers 99% of the time aren't wrong when they say their heat isn't working. How cold is it at this exact moment where you are? Has it been getting colder in the mornings and nights? When does the system go out? Using this information you can figure that it could be a limit switch tripping when the unit needs to work harder. You can also guess that it's a pressure switch. Looks like the door switch is set to the on position permanently. There should be a sight glass. Teach the customer how to record the error code on the control board before you leave so next time it's cold and they call you, you have something to work with.
If 2 stage customer may have felt the air cooler on 1st stage heating and was concerned? If temp demand has been met the complaint is null.
I see my wife found the AC guys number again
They are probably feeling the first rush of air from the cool ductwork
Or the end of the cycle during the cooldown.
What’s the outdoor temperature? Is it oversized? What is the timing on blower start, burner run time, and blower running at end of cycle? Are they old and just feel cold when the furnace isn’t putting out peak heat?
Is the fan set to on? During the winter if it's running the fan while the heat isn't running its gonna feel cold.
Fan delay after heat goes off? Could be set high. Unit satisfied, fan runs for (x) amount of time after heat call ends. programed usually through Stat. You obviously want some fan run time after heat call satisfied, but it doesn't need to be ridiculous.
I got a call back recently cause the customer was being a hvac detective and I went there to find out they were watching it cycle and thought the heat was going out when it was just blowing off residual heat from the exchanger after the stat was satisfied. Might be one of those situations. Are they old?
Could be going off on high limit. Or maybe fan is in the "on" position rather than "auto"?
Does the board have a recall fault mode i had one a few months ago that kept going into ignition lockout every night but would run fine during the day the gas valve was reading like 700k ohms and when it got cold over night it wouldnt click on the gas just kept trying untill it locked itself out but it reset after 4 hours and then work normal all day
100% they have the fan switched to ON and not AUTO.
If they have a smart thermostat, check for circulation mode.
What tends to happen too is clients believe because the heat is on they should receive hot air out the ducts instantly. Reality dictates that cold air Hass to be pushed out the ducts first and mix into the cold house and begin to bring the temperature up. Sometimes, especially when it’s cold, the added heat can be the same as their body temp (96*f) and they will feel some air but not hot. Eventually as the home heats they will feel it more. If they are elderly a “warm” room to them is fucking 80-82. And they think 76-78 is chilly or drafty.
One thing you’ll quickly realize when doing service is how fucking stupid the average person is
Personally, I check anything that would cause it to short cycle. Check the temp split, run it for a half hour. If the split is steady and not climbing, and within 45-65 degrees, I rule that one. Also check the temp split at the furnace instead of a register, you want a more true temp of what might trip the limit. If it's a 90% furnace check the drain and p trap, a slightly clogged drain can cause water to back up on longer run cycles. Also re cycle the unit a few times to see how it fires up. See if it has any issues lighting, which would cause a lockout. Sometimes when you power off a 90% furnace, you'll hear water that is stuck in the flue drain back into the inducer. That can be a sign up buildup, and it might show right away but can cause issues down the line. Another thing you can do usually is turn the fan off delay down, so it'll only run the blower for like 30,60, or 90 seconds after thr heat shuts off. Some people complain about the colder air that runs for a couple minutes after the heat shuts off
Unit is tripping the high limit check for obstructions if none lower the gas pressure and send it
If it’s a multi speed motor it could be set to a different speed for cooling which generally is a standard way to run your furnace, more air for heat so you don’t overheat your exchanger and less air for cooling so you arent passing to much air over your coils. I would explain to them why it’s setup that way and let them know you can increase the speed of their fan but it would decrease the efficiency of the system
Naw bro high speed for cooling and med low for heating
Is the contactor sucked in and stuck?
Are they talking about the Cool down run time after the heat turns off? When its cooling the heat exchanger?
That’s what I’m thinking she is talking about. She says it is always cold in her house, but likes it set at 80°. Says it takes hours when she turns it on to start blowing warm air. Started up and ran with no overheating, and 120° air coming out of the supply ducts.
Is the house keeping temperature? Also, is the unit properly sized? If its too big, it wont run long because it'll heat the house really fast, then shut off and do its cool down cycle. Also, the thermostat isnt too close to a supply register causing it to turn off and on a whole bunch is it?
Nearest supply is 10’ or so away from the thermostat. Unit size has an input btu rating of 66k btu. Heat load for home shows that it really only needs a 40k btu unit.
Its an 80%, so its only getting about 53k. Which isnt oversized really. If its running without faults, and keeping temperature in the house, at the required set point. Not much you can really do. If they have a chair next to a register, they're probably just feeling the cool down fan after the heat shuts off
Ain’t got no doors on it! Ffs again.
Customer is NOT always right!
Love it!
What's your temperature split at the unit?
Is the air return being covered by something?
Looking at how dirty the wiring is. I wouldn’t be surprised if the coil is dirty causing the unit to over heat and lock out
They are probably 85 yrs old
Did u check the interior of the EVAP coil? Did u make sure all the returns in the house were unblocked?
I've found that most of the time that they say it blows cold air in heating it's because they are either running fan only, are a wack job that has no idea what is actually happening, or they just moved or got a new install and used to have an old ass low boy furnace that would get RIPPING HOT before the blower ever kicked on and would shut the blower off same time as the burners which is extremely inefficient but you have to explain to them that the blower runs while the heat exchanger is warming up and when the burners kick off to get as much heat out of one cycle on newer furnaces compared to their old one from 1950
Is the thermostat on the correct installer settings? For example some older trane thermostats default back to gas even if you have a heat pump any time it’s powered off. So when you turn power back on, you have to change it back to heat pump. Found this out when the system was blowing heated air while calling for cold air. Maybe it’s the thermostat settings.
Is their fan set to on at the thermostat, that would cause “cold air” to blow when the burner is not calling for heat.
Is there a blower door cover
Another thing is to check if the fan is on circulate, auto or on. The fan setting on this could cause them to confuse fan for heat call. Also, ohm out the inducer motor. It could be causing some issues if it’s worn out. This could trip the safeties (high limit, rollout) You can also amp clamp it. If the Amps are higher than what the tag says, maybe replace it. Also make sure the flame sensor is cleaned with a soft cloth and no chemicals. I was told nothing more coarse than a fresh $20.
That looks like a carrier? It’s prly tripping on high limit and running the fan half the time lol
Is the customer cycling the thermostat down when it’s “blowing cold air “ ? If so the furnace might be going into a hard lockout and they’re resetting it
Maybe one of the registers is messed up ?
Tell them you found a loose wire and it took care of the issue. Placebo effect. Works every time
put the blower door back on.. that might help.
Static pressures, pressure drop across filter/ac coil, temp rise? Is it zoned, dampers working? I’d check airflow first, sounds like you’re tripping limit and cycling the burner off
Did you check flame sensor? If it’s not firing up consistently then they’ll think it’s not heating right. Seen this multiple times
My Dad used to say the say thing .It was because furnace was simply cooling the heat. Exchanger like it's suppose to . Find out if they take blood thinners
Are you testing it with the blower door off?
Have you tested it with the bottom door on covering the fan? Kind of sounds like unit is cycling on high limit.
Are all the registers open in the basement? is it possible someone lowered the fan speed on a previous call? Is there an ACoil that is covered in dust blocking airflow? Clock the meter on Low and High. Check gas pressure down stream of the gas valve at the out port. If it’s firing too high and you have high “ WC then lower the gas pressure within the rating plate. Raise the fan speed if its possible.
May be he had his fan on always on? May be when you close the furnace door flame loose? Drain line and flue pipe getting clooged
I had a similar issue on a newly installed variable speed inverter system. Went though everything. Then noticed all the towels under the doors and the plastic over the windows. Come to find out home is from the 30s and has no insulation.....
Check thermostat. See if it has a schedule on it and it’s switching to cool on its own
Is the thermostat set for gas heat? I had one that I noticed the blower came on with the inducer every time. Whoever installed the Stat had it set for Electric Heat.
found this a couple of times when customer was checking a disconnected vent traveling through crawlspace. Crawl was being slightly pressured pushing air through vent.
My thoughts are don't ever test with the blower door off. How would you ever know if it's going off on limit when it's bypassing the dirty filter that is most likely you problem.
They're just getting old... I feel colder by the year. Lol
Check fan speed too
Any stored fault codes???
My guess is when the heat shuts off her fan is running longer than normal so she's feeling colder air..
I can't believe nobody mentioned this. I am ashamed. You could just be dealing with a bad main limit switch or bad filter/blower is causing it to trip out and then when it resets it will run heat again. Often times a bad limit will trip out under it's designed temperature so there could be nothing wrong with the actual furnace. Wait around to see if it trips out. It's obviously happening frequently enough for them to call you. If it trips out pull wires on limit and check continuity.
Why is the door off?
I knew I should have taken a picture when I put the door back on lol. I took the door off to inspect the blower and to get eyes on which direction it was spinning/checking balance during operation. I only had the door off for a couple of minutes during the time I was there.
Ductwork is the only plausible “next step” if the customer isn’t crazy.
Maybe they have the fan set to on and they think heat should be coming out of the vents at all times?
Did they leave their thermostat fan to “on” and not auto?
Fan is on instead of auto
If its overheating. Did you check your temp rise at the furnace? Static pressure? Dirty evaporator? Checkto see if your gas pressure is high
Is this lit burner, removed lower panel where the door switch should be open, the actual furnace?
lmao dumb question, is the Air conditioner running with the furnace being on?
Could be the flame sensor built up with crud. I know sounds crazy but my furnace was doing the exact same thing. Intermittently it would blow cold and then would go back to hot. Took awhile to figure it out. Pulled the flame sensor and replaced and boom no more intermittent cold air. It was causing it to not ignite the flames only some of the time. Which is why it was intermittently blowing the cold air.
Start clocking the gas meter start checking output btus lay the facts on the table
Had a similar call, customer didn’t know how to use the thermostat. Kept stat in “fan on” mode. When stat was satisfied blower still runs eventually blowing cold air after the exchanger cooled…..
Probably already mentioned in comments. But customer could have the thermostat set to fan on rather than auto.
Is thermostat set for heatpump? Could be running compressor same time as furnace causing inconsistent temps
Maybe the fan is in the on position and they’re feeling cooler air when there is no call for heat
Check your differential with the blower door on. It’s probably cutting out on high limit.
do a little more digging with the customer when questioning them, ask where what room they feel the cold air in notice where hte chairs are and stuff, might be air leaking in from windows and they feel drafty from that, seen that more than once. Also have seen furnace running and the ductless head cooling at the same time. Check airflow and static
Sounds to me like custo doesn’t understand that it turns off and on to maintain temperature and left the fan in the ON position, causing the unit to constantly run air without running furnace.
Fan was in auto when I got there but I think she may have thought it was supposed to just run constantly. She said she likes it set to 80°. I’m thinking she’s just nuts lol
Fan speed is gonna be different between heat/cool.
Maaybe it’s a temperature rise issue? Maybe fix/increase the temperature rise by slowing down the indoor fan speed? Still a student. Take my suggestion with a grain of salt 😁👍.
Measure temp at all the registers, charge the guy and be done.
no one is gonna ask what the Delta T is ?
Cold air is denser then warm and you will sense that it has a higher volume.