How to wire my thermostat?

I have a thermostat with Rh, Rc, G, W, Y, but, not C. There are five wires from the wall - Red, Black, Blue, White, and Grey (yellow). I used a meter to check; the 24V is output between Red and Grey; also between Black and Grey. I put Red-Rh, Black-Rc, Blue-G, White-W and Grey-Y. The heading and fan are working. But, the cooling doesn't seem to work. Please advise. Thank you very much!

They were all working. I took out the wires without writing them down and messed up.

Attachment image

3 Answers

  • 4 months ago

    They were all working. I took out the wires without writing them down and messed up.

    You need a professional ON SITE.

    Step 1 is ALWAYS to assume the wiring colors of whatever you are removing is NOT standard and document accordingly.

    Step 2 is to check the OPPOSITE end of the wires to determine which is actually wired to what.

  • 4 months ago

    the written instructions that came with you new thermostat tell you in words how to connect it.  Kiddas has told you what the wires in the wall do ... just connect them up as the instructions say.  and if you didn't get the written instructions, they're online at maker's website -- search using brand and model number.

    that everything works except the a/c suggests the wire from the thermostat to the a/c maybe be damaged.  check both ends.  if you don't see a problem, get out your continuity tester -- you can check the continuity by temporarily disconnecting the yellow wire [with system off] and reconnecting it to the common hot line [Rh -- I think the 'h' stands for 24v hot and the 'c' for common or ground], then turning system on.  (or just bridging them with a bit of a shunt wire.)  if this starts the a/c, the line is fine but the thermostat is not.  if it won't start the a/c then you use continuity tester at the outside unit to check and see if you have a circuit ... if not, then the line is compromised and you'll need to replace it.

    Source(s): grampa
  • ?
    Lv 7
    4 months ago

    Rh Rc is a power supply to the thermostat.

    one of the Rh Rc may be the hot wire and the other may be the common wire.

    Y is the cool wire which sends a signal to the air handler to turn on the AC.

    W is the heat wire which sends a signal to turn on the heat.

    G is the fan wire which sends a signal to turn on just the fan.

    check the wires on both thermostat and air handler control board to make sure the wire matches.

    if the air conditioning doesn't work, u may need to check the Y wire and tighten the Y wire.

Still have questions? Get answers by asking now.