Thanks. I tired that and it seems to make no difference. Here is what I see when furance is tunred on.
* Blower starts
* After sometime, igniter lights up
* You hear a click (I think this is when burners are supposed to fire up but they don't)
* Ingiter turns off
* Motor kicks in blowing cold air
I did turn gas valve off and then back on to see it helps but it did not. I have not checked if voltage is OK at the valve.
Is there a possibility of water sipping into the inducer (thru flue vent on the roof) causing this type of problem? Few days back, after heavy rain, there was some water under the gas flue vent elbow on the garage floor. But hearter has been ruuning fine after that.
If there was a problem with the inducer, the igniter would not light as it would not make the pressure switch. The problem is with the gas valve. The clicking you hear, is that coming from the control board or the gas valve. My guess would be the board is clicking and you are not getting 24 volts to that valve.
Do you own a volt meter?
I don't have a volt meter but I will see if I can borrow one later today.
If Gas valve does not get 24V, does it mean control board (IFC) is bad?
If Gas valve is getting 24V, does it mean Valve itself is bad?
That would be a correct assessment.
You need to check to see is you get 24 volts from the board to the valve, if you do you have a bad valve. If not, bad board.
Check when you hear the click at the board.
Just one more thing to add to the previous experts comments...
This unit has what they call a "HALC" limit on the blower wheel housing that is in series between the gas valve and control board. If that limit is open it would also stop the gas valve from coming on... I bring this up just so that you don't miss it and potentially change a part unnecessarily.
The limit has two blue wires (along with some others) if you jump the blue wires together temporarily to test it you will bypass the limit. You can then either rule it out of the problem or may even find your solution here.... These are supposed to automatically reset if tripped so it isn't likely... but you will want to be sure before buying other parts.
Thanks! I just got back. I measured the voltage at Gas Valve and there is not much reading there (< 1 volt). Looks like control board might be bad.
Can HALC cause this?
How difficut it is to replace control board?
Sorry for the scribble above, i was trying to respond on my blackberry before I got back to a computer.
The HALC is another limit designed to cut of voltage to the gas valve so it could definitely still be the issue.
There are two blue wires on the HALC you can trace them both back to 9 pin plugs. One of these is on the circuit board. Connect your voltmeter to that blue lead (set for a 24V AC signal) and watch the start up sequence.
The gas valve will signal will only be "on" for about 5 seconds while the igniter is glowing red hot - you wont see anything outside of that short time window.
Let me know what you find and we will go to the next step then.
I was checking gas valve voltage as a DC signal.
Is that correct or it should be 24V AC singal at the valve?
It should be an AC voltage signal. It should read between 18 and 27 volts AC.
You can check from the C and R terminals on the control board (where the thermostat wires connect) to get a reading and make sure you are set on the right voltmeter scale.
I am not getting much of an AC signal at the gas valve either.
Two blue wires on HALC switch are already jumped with a white wire that is connected between them! Looks like this was done at the original installation. That takes HALC switch put the equation.
Does it mean it is a bad controller board?
My mistake - two HALC blue wires are not jumped. After another look, a white wire is connected between a blue wire and another connector on the switch which right next to 2nd blue wire. It is hard to see unless you get very close!
The two blue wires shouldn't have been jumped together, the little white wire is supposed to go to its own terminal with yellow wires on the other terminal.
If you do not get 24V AC at the blue wire, or through to the gas valve (while the ignitor is red hot) then yes that pretty much eliminates everything back to the control board.
I can give the part number and a link to buy this part online, but you will have to give me the full serial number of your furnace so that I can be sure to reference the right one. Its really not hard to replace and if you keep track of which wires go where it can easily be done by a homeowner.
It's a control board. I took a close look at it and I see a burned spot next to the LEDs.
Here is the info:
Someone quoted a $500 to replace it!
Thanks for your help.
The good news is that your furnace is new enough that you don't need the additional flame sensor conversion kits which saves a lot of time and money...
It will be a simple "wire for wire" exchange from the old board to the new board. It is part number 62-24084-82.
Now the bad news - This board is not a cheap part - but is still allot better than the $500 you were quoted.
Most of the time I refer people here: ($287)
Also it is on ebay: ($250)
Best of luck and if I can be of any further help please feel free to contact me.