help on a gas furnace ignition problem

zorroo

Our gas furnace stopped working. The problem is when the thermostat calls for heat, everything looks normal from beginning: the induction fan starts to spin, then the Hot surface ignition comes on. The problem is now there is no flame comes on. It looks to me the gas valve does not open at all. The ignitor comes on for three times and stops trying. I did not see any broken wire.

I don't have much experience here, so any suggestion is helpful. Thank you!

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kennzz05

are you sure you have gas (if lp gas) and is gas valve on

kennzz05

ok well i see gas is on so is it lp?

zorroo

It is natural gas I think since we get the gas from the public gas line.

kennzz05

make sure gas cock is on if you have a meter see if you have 24 volts at the gas valve after the ignitor starts glowing (it may take awhile) if you have voltage at the valve and your sure you have gas, the valves bad,
you can double check to make sure you have gas by slightly opening the gas union and see if you hear/smell gas

don seabrook

I have the same problem, the flame seems to come on for a second or so then goes out. Do i need a new flame sensor?

kennzz05

youve got a differant prob he gets no flame
you need to clean your flame sensor, remove it and sand it lightly with fine sandpaper or steel wool and make sure its engulfed by the flame when units running

flacens

i have the exact same problem....the exhaust fan starts up and the pilot lights up, but the heater never comes on, and the burner never lights up. i suspected a bad gas valve....is that it or could it be something else? i know for sure i'm getting gas because the heater worked fine for two days, but hasn't worked for about two weeks now

kennzz05

your problem is differant also, he dosent have a pilot
suspect dirty pilot switch if its carrier look into replaceing it if its the 3 wire type pilot switch

flacens

yes i saw three wires connected to it from the valve box. I had done some research and found that it could be something called the thermocouple? could that be it also?

thanks in advance

flacens

the pilot will stay lit until i turn off the heater

flacens

sorry i'm not very knowledgeable in this area but just to give as much information as i can...

i am getting gas to the valve but the heater won't ever release the gas to the burner....if that makes sense

kennzz05

if you have spark ign...(tick,tick,tick,tick,tick) and its a carrier than replace the pilot switch. you dont have a thermocouple. the pilot switch can sometimes be cleaned, but its not always going to work. i think they run around 25 dollars if you can find someone to sell it to you

flacens

ok thanks for your time. i'll check the pilot switch!

flacens

FYI it's a honeywell sv9500....here's some pics







the valve is off in the picture, but i had it on when testing it