I'm trying to help out my neighbors; they're elderly and on a fixed income. I have handyman experience with HVAC but am not schooled. Their Trane furnace doesn't heat, although the AC works. I've already changed out the control board, a 50A65-5165. After I changed the board out, the inducer fan came on, the pressure switch circuit closed, and that was it. It did not time out; the inducer would keep running but the ignitor would not glow. I put my testers on it and it was getting approximately 68 volts (it's an 80 VAC ignitor, and the board instructions say it has to be a White Rogers because the board senses the lowest temperature at which it will ignite gas. I replaced the ignitor, and got the same results; it would not glow. I checkd for continuity through all the limit and roll-out switches. I thought maybe some wires were misplaced on the board so I pulled the spade terminal wires and made sure they were on the proper (marked spades), and now I'm blowing the 24V 5Amp fuse whenever I call for heat. The AC still works. I'm mystified - I think somehow the board has decided 68 volts is enough for the ignitor but it isn't, but I don't know why all of a sudden I'm blowing that fuse (immediately) when I call for heat. Any geniuses out there?
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