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Gas furnace just barely does not work.

3K views 9 replies 3 participants last post by  Halcyon 
#1 ·
The thermostat calls for heat. The first motor starts. A few seconds go by and the pilot clicks, igniting the pilot light. About 30 seconds goes by and the blower turns on, blowing air throughout the house that is only being heated by the pilot light, the burners never turned on.

I had a problem before, no gas was making it through the smart valve. I disassembled the valve and found that somehow a small, hair-thin thread of copper wire had become detached from it's terminal. I soldered it back on and we had heat for about a week. Then this begins. I already checked the smart valve, tested all wire terminals for continuity and made sure the limit switch wasn't thrown. Does anybody have an idea why the burners wouldn't turn on even though everything else does?
 
#8 ·
I haven't been reading any current across the mv/pv wire from the valve. Should the valve be sending current to the board through that line or should the board be sending current to the valve? Or am I way off and looking in the wrong direction? (This valve has three wires, one MV, one MV/PV/ and one PV. The single MV & PV wires show readings of 24v across them when everything is running)

I know everyone likes to say that they're competent and the warnings the pros give them don't apply in that scenario, but if it is the valve; I've repaired them before, even had to install a rebuild kit in a valve once(which was a lot easier than fixing broken solder points).

So I know my way around the valve, but that doesn't make a pro, and I would never say as much, that's why I'm here! I only bring that up because if you can offer some guidance as to how to go about repairing the valve, I want you to be comfortable telling it to me and knowing that I won't get myself killed.
 
#9 ·
Mv is power to the main valve from the board, Pv is power to the pilot valve from the board, Mv/Pv is the common grounded side of the low voltage transformer. You should have 24vac on Pv, Mv/Pv first and then Mv, Mv/Pv after pilot is proven.
 
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