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I tried the furnace only, raised the temperature and nothing came on. I tried the fan only and nothing. There is nothing registering on the control board in the furnace, no lights, no anything and there is current through the board.
I took the door switch out and checked the contacts etc.
No matter what there should still be lights on the board right, no matter what? If there is power the board would reveal fault lights, etcetera, no? Only a bad board would show nothing I imagine.
What would stop the control board from showing any lights when there is still power to it, does anything interrupt it completely?!
Tried the fan only, nothing. Tried the furnace, nothing. There seems to be no lights at all registering on the control board. There is no transistor hum. There is no noise from the exterior fan. There is power going to the control board but no lights. There isn't a peep of a sound anywhere from any device in the chain. Is it a bad board?! I mean what else would cause such a nothing response and no error lights or lights of any sort on the control board? There is power going to the 120v furnace switch. Would a bad door switch allow current to the board but still show no lights? Boy is this frustrating... Thanks all.
I checked all of the available Honeywell information. Checked the voltage to the cabinet switch and beyond. AC was working fine and just quit out of the blue. And what would cause the control board to stop registering any lights whatsoever? I ordered a new board....
If there is power to the board but there are lights on the board that are supposed to illuminate that aren't, it sounds like the fuse on the board is blown or the board went bad. Lightening is usually the cause. I believe many of the boards actually run on 24v provided by a transformer though so you wouldn't see 240v to the board. Typically the thermostat will call to the board and then the fan/timer delay relay will be activated. Once the delay time is reached, the relay will switch and send power to the fan motor run capacitor and kick the blower fan on. This is all stuff that would be shown on the schematic/wiring diagram.
It is hard to diagnose a HVAC system without being there hands on. You need to study the diagram and see where the power travels and what voltages. Then start following the path with a voltmeter. It isn't really all that complicated if you have a little electrical, electronics and schematic knowledge. You just trace the path checking until you find the break in the system.
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