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I had a furnace installed about a year ago in my basement. The installer left the wires sticking out of the wall for me to install a thermostat. He said if you want to turn the furnace on, just touch the red and white wire together. This has worked for me for the last year when I wanted to warm up the basement I would just hook the two wires together.

The day came when I was ready to install a thermostat, I hooked up the 5 wires to the thermostat the way I thought it should be installed. When that didn't work, I tried many other configurations. When none of them worked, I decided to go back and check the red and white wire test by holding them together. Now the furnace won't turn on at all when I do this.

Things I've tired

  • I made sure my furnace was all closed up and the safety switch on the furnace cover was pushed in.
  • I made sure the furnace power switch was on.
  • I made sure the main breaker was on for the furnace

I am wondering if some of my wiring configuration might have tripped something in the furnace control board. I noticed a small button on the control board and was wondering if this might be some sort of "Reset" button. I haven't tried it yet, because I didn't know what it did.

Any advice would be appreciated on getting my furnace working again and hooking up my thermostat.

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  • What type of thermostat are you trying to install? If it is one that requires the C or common wire for operation, then it may not be hooked to the furnace control board.
    – Mnc123
    Feb 19 '15 at 17:21
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    Including the make and model of both the furnace and thermostat would help. Also including what wire combinations you tried.
    – Tester101
    Feb 19 '15 at 18:33
  • If you're lucky the transformer is fused, and you'll just have to replace a fuse. If you're not, you might have to replace the transformer.
    – Tester101
    Feb 19 '15 at 18:33
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    He could have blown the 3 Amp fuse on the furnace control board if 24v was introduced onto Common. Opening the furnace and checking the fuse will rule this out. If it is blown then you can replace it with any automotive style 3 amp fuse that is the same size frame.
    – Mnc123
    Feb 20 '15 at 0:57
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Jump red to green and see if the indoor blower runs, if so you have 24 volt power and the transformer and 3 amp fuse on your circuit board are fine,if not check the 3 amp automotive type fuse found on your circuit board. If you have no fuse the transfomer may be bad from touching red to Common a direct short which fries the transformer. Is there a diagnostic light on your furnaces circuit board? if so is it flashing or staying lit? is there correct high voltage as well as the 24 volts? Breaker tripped?

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