PDA

View Full Version : Furnace will not light



jsarin1
09-27-2012, 03:19 PM
I have a tempstar furnace with a honeywell smartvalve system. The ignitor will not get red hot to light the furnace.
I replaced the thermocouple/ignitor with an equivalent one (Honeywell Q3400A1040 Replacement Ignitor) and it still did not light.
Then I suspected a gas supply problem. When I turn the valve to On, I heard no gas coming through. So, I ordered a replacement euivalent (Honeywell SV9500M 2682 Gas Valve). I can now hear the gas come through when it is turned on. But, even so, the ignitor doesn't light. Any advise would he appreciated...

jsarin1
09-27-2012, 03:25 PM
I forgot to include that the furnace is getting electrical power. The blower spins when you turn it on and at the thermostat. According to the thermostat it is calling for heat. I changed the batteries, but that did not change anything. I've had to furnace on for about 20mins and it still will not light.

I just found another ignitor/sensor in the garage from the previous homeowner. Put that one in and still no light.

jimbo
09-27-2012, 04:37 PM
Probably a bad ignition control board. Pretty common replacement in gas furnaces.

jsarin1
09-27-2012, 06:46 PM
I have a Honeywell circuit board labeled ST9120C 4040. Is this circuit board equivalent to an ignition control module?

jsarin1
09-27-2012, 07:00 PM
17388

Took a photo of the lower compartment as reference.

jimbo
09-28-2012, 03:08 AM
That is a fan control relay board. Probably not what you need. You need a wiring diagram of your furnace, and probably a service call from an HVAC tech.

DaMan
10-23-2012, 12:17 PM
I have a tempstar furnace with a honeywell smartvalve system. The ignitor will not get red hot to light the furnace.
I replaced the thermocouple/ignitor with an equivalent one (Honeywell Q3400A1040 Replacement Ignitor) and it still did not light.
Then I suspected a gas supply problem. When I turn the valve to On, I heard no gas coming through. So, I ordered a replacement euivalent (Honeywell SV9500M 2682 Gas Valve). I can now hear the gas come through when it is turned on. But, even so, the ignitor doesn't light. Any advise would he appreciated...


If you have replaced the gas valve and igniter I would suspect the logic board. Most logic boards go through a start-up procedure. If something goes wrong during the start-up procedure, your igniter will not ignite or your gas valve will not open. If your igniter will not heat up, that means no electricity is going to it from the logic board. If your gas valve is not opening up, that means your logic board is not telling it to open. Everything points to your logic board. This same thing happend to me on Christmas EVE while it was 19F outside. I did not notice the furnace quit on me until I woke up on Christmas EVE morning and the house was 59F inside. I poked around inside my furnace and my logic board was dead. It got power to it, but did not provide power to anything else. Not fan, no igniter, no gas, just dead.

DaMan
10-23-2012, 12:23 PM
17388

Took a photo of the lower compartment as reference.


That looks like the correct board. You can see the Common,Green yellow, white, and red connections along with the fan and other controls. Unless their is another logic board inside the furnace, I would suspect this to be the main board.