Originally Posted by dryflie
J. So no ignition click for sure. As for the gas valve I can't say I've heard anything. I've hit the on/off switch at the furnace, topped out the T-stat, and sat outside to click the On/off switch on. Nothing but cold air from the exhaust. No gas smell. So perhaps the Board is faulty??
From krazedave it appears the board testers are not total fool proof.
If you have no gas and no spark, while not impossible, odds are low both of those systems would die at the same time unless the board is bad.
If you have a voltmeter or even a 12 volt test light you can try the gas valve for power. If no power when it is suppose to start then the board is not sending it or a loose wire connection.
The other thing to try and confirm this before buying a new board is to confirm the 2 safeties are met telling the board to start the firing/gas sequence.
There is a sail switch (in the blower housing) which is in series with a overtemp switch. I do not have 100% confirmation on the 8500-III series however the 8500-IV and the 7900 series uses a white wire on the safeties. So if you look on the PC board connector plug there should be these 3 or 4 wires in the plug connection to the PC board.
Red = gas valve power
White = the safeties signal, A series connection from the sail switch and over temp
Black = the ground (neg - 12 DC volts)
Black = A 4th could be a remote flame sense sense feedback. Yours may or may not have this.
Those wires above are on the plug strip.
There is also a igniter wire coming off the board but it connects to the ignition coil not the push on multi wire connector. Careful of that igniter wire, it will feel like a spark plug wire getting you if it is live. 10,000 volts jumps an inch so do not grab that one.
If the white wire has power going into the board, it starts the whole firing sequence. If no power then the sail switch or overtemp switch has issues or a loose wire. You can test with a 12 volt test light or a voltmeter.
Basically, If the safeties are giving the board 12 volts and the gas valve does not have power after the timeout period, odds are high your board is toast. On the 8500-III with the separate timing relay for the blower purdge, the board should fire fairly quickly after getting the safeties power.
Hope this helps and let us know how you make out.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
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