I have this split body A/C, that I haven't been able to turn on this season, when I noticed the thermostat does not draw any voltage, after days of troubleshooting I noticed that the previous owner disconnected this wire from condenser, (they used window a/c to save money).

Now I have to connect this wire back to control circuit in the condenser. This 24 vac line has two wires: yellow and red, and control wire come out of condenser has blue,pink,and white, how shall shall I connect them ?

I have enclose the contactor picture as follow, thanks for your attention. The power line come up in the middle, control line goes down to the right bottom leads to air handler. That disconnected 24 vac line is not shown.

http://im1.shutterfly.com/media/47b9...D550/ry%3D400/

If it is bttween the blue, pink and white, I would disconnect the blue, pink, and white
Then set thermostat to cool, you should look for 24 volts AC on 2 of the 3 wires. Remember or write down the 2 colors, turn unit off and connect to the wires going to the Contactor coil(brown and purple)

Also check that copper is not exposed where the purple and blue wires connect at wirenut.

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Originally Posted by Stratmando

If it is bttween the blue, pink and white, I would disconnect the blue, pink, and white
then set thermostat to cool, you should look for 24 volts AC on 2 of the 3 wires. Remember or write down the 2 colors, turn unit off and connect to the wires going to the Contactor coil(brown and purple)

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Thanks for the reply, but the voltage bearing control wire is not yet connected, there won't be any voltage across any of the control lines. I can trace the white and pink lines go to the thermostat, and blue line goes to the relay next to air handler motor.

You need 2 conductors to contactor coil, 1 from thermostat, and the other side of transformer is gotten from thermostat or air handler, you will see 24 volts between the correct 2.

Thanks will try this

I see blue and white connected in the condenser and red(pink) taped off. This is fine.

One of these wires goes to Y of the tstat. Doesn't matter which.

The other goes to common (C) on the transformer. This could be tricky to find.

Thanks for the reply.

Both pink and white wire connected to the tstat, actually the white wire goes to the Y terminal on tstat, the blue wire goes to one side of blower relay;

Yellow and red transformed line (not shown in the picture) were not labeled at transformer, how can I test which is common ? And how do I connected these two wires back to the condenser in the picture ?

You are using blue and white at compressor and pink and white at thermostat. Need to use 1 pair only.
I usually see the compressor control wires go to Air Handler, also Thermostat wiring between thermostat and Air Handler.
Whad do you have between T-stat and air handler? I would hook blue from thermostat to compressor contactor coil. With out any testing you can hook other wire to either transformer wire 50/50 chance, it will work or it won't, then it is other wire.
A meter will show 24 volts between blue and white when set to cool.

HTML Code:

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<pre>

              [relay for a/h]      [contactor coil]
                      o    o            o    o
[tstat]              |    |            |    |
                      |    |    blue    |    |
blue  o---------------+    +-------------o    |        o-------- yellow
                                white        |          24 vac  to be connected
white o----------------------------------------o        o-------- red
                                pink
pink  o--------------------------------------------o




Here's basic schematic for control wires, as you can see, b/w tstat and air handler
there's only one relay.
</pre>

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I usually see a red wire (24 volts from transformer) to thermostat Red, then when you select cool, the red connects to green for the blower fan relay, and blue for cool(compressor contactor)
The white from thermostat to air handler is usually for heat.
Blue usually doesn't go to relay then contactor unless it has a circuit board.