Furnace intermittently working.?

Question

When our Carrier gas furnace turns on it kicks the flames on for about 15 seconds or so before turning back off and repeating process 3 times. After failed 3rd try a blower and/or fan turns on for a couple of minutes before turning off. If I disconnect then reconnect the main power to furnace then the furnace will starting working properly for a couple of hours sometimes.

Things I've checked or have eleminated:
filter
thermostat
Gas valve turned on
ignitor (turns bright orange/white like normal)

Has anybody experienced this as well? Are there any other checks I can do before the repair guys? Thanks

Answer 1

It's probably not the thermocouple. Disconnecting and reconnecting the power to the furnace would probably not cause the thermocouple to start working again if that was the problem. The thermocouple is a small device that shuts off the gas in the event that there is no heat (or flame) when there should be. This keeps you from accumulating a whole bunch of gas in a case where the flame either never starts or is somehow unexpectedly extinguished.

Could be wrong and I am including a couple of links below for you to attempt to replace the thermocouple just in case. (It's a fairly easy procedure.) If a thermocouple is on its way out, it might be a coincidence that its refresh is occuring at the time you are powering off and on again.

The secondary fan that is running for a few minutes between cycles is trying to discharge (in the chimney/vent) what it thinks may be unburnt natural gas.

Here are some other possibilities:
(1) high temperature security sensor has gone bad. This is a small device that would stop letting current flowing through it in the event that your furance experiences a flame flare-up. You can usually trace the wiring of this device which will be found generally above the burner comparment, yet still accessable.

(2) some other gas sensor or pressure sensor that is wired in series with (1), above. Generally these components are acting as switches and will close the circuit if they want to complain.

You can isolate them as an issue by disconnecting them and bypassing them. Note however, that this is a TEMPORARY measure and should only be used to diagnose that the component has gone bad. Its kinda the equivalent of putting a penny behind an old blown fuse. If you are able to isloate one as a problem you can order a new one from an HVAC supply house or... in some cases a Home Depot or Lowes. Or at least, you'll make the HVAC repairman's visit a lot shorter (and hopefully cheaper.)

Good luck.

Answer 2

I believe something is causing furnace control to lockout, if the furnace faults on or during operation the control will try 3 times ,then locks out completely until power is turned off then on to reset board. reset unit, wait until unit cuts off, try to find a small window on the door, usually you can see a blinking light on the furnace control. count the flashes, usually the codes are found on the inside of blower door. may give you an idea of whats going on.. hope this helps..

Answer 3

get some sandpaper and sand down the thermal coupling. It's really called a flame sensor. It will be moUNted in the flame .. un plug it and take it off of the furnace and sand it down re attach it and wella

Answer 4

Sounds like the blower fan is going bad and drawing so much current it times out.

Answer 5

Sounds like a thermal coupling to me and this is definitely something left for a licensed gas guy (or gal)... you don't want to blow up your house because you messed with a gas fixture...

Answer 6

the first problem u have is that it is a carrier .they have three relays in that unit [trust me i know] your problem is the fan relay!!