Who Needs Heat?

A few weeks ago my furnace stopped working. The fan would come on, the flames would light the burner but the large blower would not turn on to blow the air throughout the house. However it would work if i switched the thermostat from "auto" to "on" but this meant that the blower would run constantly.

There are a lot of pieces in there. The blower is the big metal thing at the bottom.
furnace wiring, circuit board, thermostatSo after a week of reading online i figured it had to be one of these things:
  • blower control board
  • heat sequencer
  • temperature limit switch
  • fan limit control switch
  • temperature sensor
  • relay switch
Then i realized that my furnace was a newer model and half of those things were all incorporated into a circuit board (the blower control board). At the furnace i could hear something click when the blower was suppose to come on but nothing happened. I checked many things with the volt meter but everything seemed ok until while switching the power on one time i notices something spark. It was coming from the relay that turns on the blower, on the circuit board. So i took a bunch of pictures of the wires so i would know where they plugged back into and remove the board. Sure enough there was a burned spot on the back cover where the board was shorting out. furnace, heater, shorting out, wiring,
The shorted out board behind the blower relay switch.
furnace circuit board, shorting out, relay switch, solder
I soldered the wire back to the connector, hooked everything back together and amazingly enough it worked, the blower came on when it was suppose to.
resolder circuit board, furnace, wiring

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