My dog has chewed through my wires on my unit that turn on my fan at the ac unit. This is not the first time. Its always been an easy fix until now. He actuall pulled the wire from the unit and I dont know exactly what wires im supposed to connect. The wires coming from the house are red and white. But when I take the plate cover off the unit... the only wires exposed are blue and yellow. Are the the correct wires? And what connects to what.????

  • 1
    You're only fixing the symptom, not the disease. For goodness' sake, run the wiring thru a conduit the dog can't chew! Apr 26, 2016 at 15:11
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    Save yourself the risk of further damage -- pony up the $$ to have a pro fix it, and while he's there ask him for a schematic. Apr 26, 2016 at 15:12

3 Answers 3


Wire colors with HVAC wiring are non-standardized, so the colors themselves don't help much.

Your furance/air handler should have a control board with terminals labelled R, W, Y, G and C. There should be an existing wire that connects to all of these (though maybe not C) that goes to your thermostat.

If anything is different in your setup, please update your question with a picture explaining, don't just wire it as I described or you may damage something.

The A/C unit wires connects to Y and C (usually white on C, but it doesn't really matter).

For reference:

  • R = power (24VAC)
  • Y = cooling
  • W = heating
  • G = fan
  • C = common power (24VAC with R)

Since this happens a lot, I'd also highly recommend putting some mechanical protection on this wire. Since it's already disconnected, it should be easy to fish through now.

Some flexible ENT tubing might be the easiest option:

enter image description here

1/2" rigid PVC conduit could also work, you can get elbows and other connectors.

enter image description here enter image description here

All of this should be available at your local electrical / big-box hardware store.

  • I tried looking at the control panel... but its old and some is missing. If I post a pic would that help???
    – melissa
    Apr 26, 2016 at 13:16
  • How can I post a pic?
    – melissa
    Apr 26, 2016 at 13:30
  • @melissa edit your post and click the image button, or upload it to an image-hosting service like imgur.com and post the link as a comment.
    – gregmac
    Apr 26, 2016 at 13:34
  • @melissa post the photo somewhere public (e.g. imgur.com) then paste the URL of the photo into your question (use the edit link below the question) - someone with sufficient reputation will then insert the photo. When you have a tiny bit more reputation here you can insert pictures directly yourself. Apr 26, 2016 at 13:35

Your dealing with low voltage AC so you don't have to be concerned with getting the + and - backwards. Assuming the yellow and blue wires connect to the coil on the contactor, you can safely connect the two wires from the house to the two wires in the outdoor unit. Prior to doing any work with the wires, verify you have 1) the power off to the furnace/air handler and 2) the power off to the outdoor unit. #1 will keep you from potentially having to replace a blown low voltage transformer and #2 will help to keep you from killing yourself while working in the outdoor unit. The included image is representative of what I believe you have. enter image description here

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    Yeah but you could easily blow the electronics with reversed voltages. Apr 26, 2016 at 15:11
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    So which coil terminal is + and which is - on the contactor?
    – bigbull15
    Apr 26, 2016 at 15:30

The + is yellow, and the- is blue in your case (technically common, or C). The dog could have blown the fuse. There is a 3amp fuse on the furnace control board that protects the low voltage side. If you don't get anything to come one, check that fuse.

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