Gas furnace burners won't stay lit for more than a second or two

[mouppe]

Just wondering if any FOGgers could help with an HVAC question since it's Sunday afternoon and it's going to be cold tonight. My gas furnace burners won't stay lit for more than a second or two before dying down. The pilot light stays lit. I have set the thermostat comfortably higher than the current temperature to try to force the gas furnace to stay on but it's not helping. I haven't noticed the problem before today.

I have a wood fire and a couple of gas fires that are working well so I can wait till tomorrow before getting making a service call but I thought I would pose the question on the FOG to see if there's an obvious explanation.

Richard.

 

[peter halle]

I'll guess.  Sounds like it could be a bad thermo coupler or flame sensor.  Have had those go bad with my gas grills.

Peter

 

[mastercabman]

I'll guess.  Sounds like it could be a bad thermo coupler or flame sensor.  Have had those go bad with my gas grills.

Peter

That's what i think too

 

[lambeater]

Richard does your furnace have a venter motor on top and a standing pilot. If so the sequence should be Thermostat kicks in, venter motor starts, then after time  out gas valve should click, burners light, flame runs across to the flame sense probe sends a signal to the valve to say all is good and flame stays on. So all you may have to do is remove probe, clean it, put it back and all should work. Some times the slots in the burners get dirty and need cleaning as well. If you get stuck I could possibly talk you through it over the phone.

thx
Lambeater.

 

[fatroman]

I'll suggest taking a look at the thermocouple. Had the same scenario last year. Shut everything down so it wouldn't try to fire up while I worked on it and grabbed some sandpaper. Even though the thermocouple didn't look dirty to the eye, it apparently was. A little action with 220 and it was ready to go again.

 

[mouppe]

Yes, I think that's what it is. It's certainly an electric pilot light ignition system, and there doesn't seem to be a gas flow problem as my gas fires are working fine. Checking the serial number of my furnace suggests it is approaching 20 years old, but it looks to be in good shape. We have it maintained two or three times a year.

Is the probe cleaning something I can or should do myself, or is it advisable to call a technician tomorrow? I'm not an expert on gas at all (other than the curry-related type!).

 

[lambeater]

Richard give me a call at home and I will talk you through getting it to work. I'm home now 250 376 4947

thx
Lambeater

 

[batmanrobin]

check your thermostat also to make sure its working properly

 

[mouppe]

Well the problem has been resolved. As well as a faulty ground wire to the flame sensor, I had an airflow problem to the furnace. The air intake pipe was not sloping down so I had a water build-up in the pipe which was restricting airflow causing the furnace to switch itself off. When you went outside you could hear bubbling in the pipe as the air tried to pass through the water.

Of course, now that the gasman has been to re-align the pipe and the water is flowing through properly, the plumber is coming to replace the same cracked pipe further downstream which is leaking all over the floor of the furnace room!

Oh the joys of a Canadian winter!