A/C or Furnace (fan) will not come on

3015 Views 6 Replies 3 Participants Last post by texas115115, May 3, 2009

robmaxfli

Discussion Starter · May 2, 2009

The thermostat is a fairly new digital one that runs on batteries and I have verified that the thermostat is working. I tied the wires on the back of it (to bypass the t-stat) and nothing still came on - fan or A/C unit. I can hear the T-stat click when I lower the temp on it - but that's it. There are no tripped breakers or fuses at the panel. I checked for loose or burnt wires and don't see any.
I am not sure how to verify that everything is getting power as it should. I have a Ducane Gas furnace (blower) that has a Honeywell circuit board on it. I have a multi-meter but am not sure what to test and where.

thanks Rob

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qbert

· #2 · May 2, 2009

test for incoming power at furnace.Test for control power 24v at control board r-c make sure the door switch is in on ducane i believe all you have to remove is middle door section. no power, test incoming on xmfr 120v and secondary 24v. If power is good leaving xmfr look for a small fuse on board.

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robmaxfli

Discussion Starter · #3 · May 3, 2009

Well, I looked at the circuit board and sure enough there was a 5A fuse that was blown. I swapped it out, the unit came on and then immediatly blew the fuse again.
Any suggestions?

thanks

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qbert

· #4 · May 3, 2009

good indication you have a low voltage short disconnect all tstat wires and replace fuse

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qbert

· #5 · May 3, 2009

qbert said:
good indication you have a low voltage short disconnect all tstat wires and replace fuse or disconnect all tstat wires from furnace and tstat and ring out wiring with multimeter make sure wires are not touching:yes:

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qbert

· #6 · May 3, 2009

If continues you will need to trace the low voltage circuit further for shorts. You can follow the diagram on panel door.

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texas115115

· #7 · May 3, 2009

Qbert is right about wire digram

But I would look at the t-stat wires for bare spots. Although when you installed the new t-stat you probley let two wires touch and just need to space them out. Good luck.

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