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Author Topic: Carrier Suddenly Won't Heat  (Read 2453 times)

Offline al10

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Carrier Suddenly Won't Heat
« on: December 14, 2017, 03:00:50 AM »

Carrier suddenly won't heat, but air conditioning is fine.  Fan works, auto works with air conditioning, not heat.  Thermostat number seems stuck around 70 degrees.  It is a mercury thermostat.  Cannot afford service person right now and it is cold, need heat.  Thanks.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #1 on: December 14, 2017, 09:27:36 AM »
Please note that I am not a pro at this.

I think you will have to give more info. re model numbers, symptoms etc .

I am assuming that the furnace does not fire up.
If it does for a short time then shuts off without the fan coming on then you need a new temperature regulation module on the furnace.
I am not sure that is what it is called but it turns the fan on once the heat exchanger reaches a preset set point. Also keeps the fan on after the furnace shuts off until the unit is cool.

I am not sure what you mean by the thermostat is stuck at 70.
If this is mechanical (you physically cannot adjust it higher), then I would say that the thermostat is toast.

You could figure out which two wires are for heat and then short them to see if the furnace fires up or remove the cover and gently move the mercury switch till it closes.
If the above works then replace the thermostat.

If this is an older furnace check that the pilot is on.
If not then it may just need relighting or a new thermocouple

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #2 on: December 14, 2017, 03:51:47 PM »
Thanks for taking time to reply.  The ac works fine on auto and on fan.  The heat doesn't work on auto, on fan, the fan runs but there is no heat. As far as I know it is electric, just had a filter change recently.  How can the heat get running, either on auto or on fan?  Cannot afford service person and it is bitterly cold below freezing.  Parts appear to be fine inside the thermostat, it was running fine until it wasn't.  Only a few recent hesitations when starting every once and awhile.  I can turn it the dial up all the way (it is the square box style thermostat), nothing happens, it seems to think it is 70 degrees and won't do anything to change it.  Any advice would be appreciated, thanks again. 

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #3 on: December 15, 2017, 03:27:19 AM »
As far as I know it is electric
I do not want to insult you but if you are not sure if the furnace is electric or gas then I do not think you are suited to start digging into the unit to repair it.
Perhaps you have a friend who can help you out.

If it is in fact electric try flipping the circuit breakers for it on/off a couple times.
They should be ganged re: 240 volts.

Also check if there are separate breakers on the furnace itself.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #4 on: December 15, 2017, 08:10:54 AM »
Maybe I said it the wrong way.  The unit was here prior to my arrival and there have been no major issues before, it is electric.  I have tried turning the circuit breakers off and back on.  The air is on a separate circuit breaker and is fine.  When I turn up the thermostat, I noticed there doesn't seem to be a spark of electricity, I checked inside for dust, etc., it seems ok.  I don't know anyone to help, nor can a major repair be afforded.  You are great experts, and I was just asking for advice.  Thanks.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #5 on: December 16, 2017, 08:21:09 AM »
Really need a model number and even with that I may not be able to find tech (wiring) info about it.

Also electric furnaces run on 240 volts AC which is lethal.
Unless you know what you are doing it could cost you your life!!!!!!!!!!!!!

You would also need and know how to use a volt meter to troubleshoot this.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #6 on: December 17, 2017, 08:17:21 PM »
Couldn't find anything but on the thermostat cover if that would help.  I'd been running the fan off and on, a few moments ago, the auto cycled on by itself but I had to turn it off because an electric burner element on the stove which had been used for heat and cooking blew in one spot.  Hopefully unrelated.  Please detail what you mean by lethal?  It is a furnace/central air combination, what is lethal?  Thanks.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #7 on: December 18, 2017, 05:22:26 AM »
Usually the voltage at the thermostat is OK. It is low voltage AC.

The voltage in the furnace will be 240 volts.
The same voltage as used in an electric stove.
If you touch each side of the line with your hands then there is enough voltage to kill you.

I do not know what "Couldn't find anything but on the thermostat cover if that would help" means.



« Last Edit: December 18, 2017, 05:25:41 AM by manden »

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #8 on: December 18, 2017, 11:48:56 AM »
Perhaps try a Google search for "electric furnace" and then look in the videos or just go directly to YouTube and search there.

A video will probably be of more help than me at understanding the basics.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #9 on: December 19, 2017, 01:17:30 AM »
I couldn't find anything like a model number anywhere but on the thermostat cover.  Yes, I have viewed videos, etc.  The furnace started once by itself yesterday but had to be shut off because the element on the stove suddenly malfunctioned while cooking.  Would you know anything about them also?  Thanks.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #10 on: December 19, 2017, 12:18:52 PM »
Yes I know some stuff about stoves.

Unplug or remove power from the stove.
Remove the element from the stove top.
Measure it with a meter to see if it has resistance.
If not then it needs to be replaced.

If it actually blew out part of the element then it will need replacing.

Note that this does not ensure a fix as it may of also have blown the controlling infinite switch.


Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #11 on: December 20, 2017, 08:09:05 AM »
Appreciate your answer.  The element fell into pieces, fire fused the ends where the break was, together.  The burner on light will not go off even though it should be off.  Does it sound like the infinite switch needs replacing also, or is it something else?  The stove is off at the breaker, therefore no cooking can be done.  Would you have any ideas as to why the element blew and caught fire?  Never any problems before.  Thanks.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #12 on: December 20, 2017, 08:14:25 AM »
Yes it sounds like the infinite switch will also need replacing.

Also check where the element plugs in to be sure that it also has not been fried.

Elements last a long time but eventually they do blow.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #13 on: December 21, 2017, 01:16:54 AM »
Thanks for your expert help.  The element is in pieces, where it plugs in, it is hard to tell if it is damaged or not.  Looks ok from the outside but may have interior issues.  Is it possible to shut off the switch, or isolate it and still use the rest of the stove?  It is still shut off at the breaker, and stove cannot be used at all as is.  How difficult would it be to replace the infinite switch, is there a quick solution?  Do you think this happened by itself or was caused by an overload of the furnace trying to run (which it has stopped doing again), it was shut off when the element blew.  One thing after another......

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #14 on: December 21, 2017, 07:15:04 AM »
If it is a stove with older style elements (not a glass top) then you should be able to remove the elelemnt and the stove should be OK to use.

Replacing the infinite switch is usually not that difficult you just have to figure out how to access the control panel.

The furnace problem had nothing to do with the stove element blowing.


Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #15 on: December 21, 2017, 07:38:37 PM »
Thanks again.  Yes, it is an older style element, not a glass top, if the model number helps, I have it.  I removed the element straight away but the on light is on until the stove is turned off at the breaker.  Looked at the bracket, it seemed ok, maybe not.  Since the element itself isn't keeping the light active, not sure if heat is still coming from the bracket, there is no way to run the stove without replacing the infinite switch first?  Hopefully there is.  Can't afford it, have to find one, no time to.

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #16 on: December 22, 2017, 03:24:50 AM »
The infinite switch has a separate switch in it that closes and turns on the light when the infinite switch is turned on.
It does not monitor heat.

Therefore you can run the stove safely as long as the element is removed.

Just double check that none of the other elements are on.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #17 on: December 22, 2017, 09:38:29 PM »
Thanks, I will try turning it on again to take a look.  Thought I felt a lot of heat coming from where the element plugged in.  Of course, I tried removing anything left from there, could something else make the plug heat up like that?  If that is the case, what should be done? 

Offline manden

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Re: Carrier Suddenly Won't Heat
« Reply #18 on: December 23, 2017, 05:57:27 AM »
I guess it is possible for the element plug to generate heat when the element is removed but I have never seen this.

If it is doing this then the element. infinite switch and element receptacle will have to be replaced.

Offline al10

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Re: Carrier Suddenly Won't Heat
« Reply #19 on: December 26, 2017, 06:07:09 PM »
Not sure, there seems to be a little heat coming from the side where the burner was.  It could be the back burner on that side or the switch.  Is there any way to use the stove without immediate repair by somehow turning off power only to one side of the stove?  The light constantly on is a concern.  Also would you have any more ideas about the furnace?  It will cycle on normally by itself every once and a while now (if the room temperature is high) but it is below freezing in negative numbers.  Thanks.