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J Russell
Jun 14, 2013, 03:00 PM
I have forced air AC with a condenser outside. The problem is that I have no power at Y on the control board output to the condenser. Does the wall thermostat control this function? The transformer is good as it tests 24 volts at R on the control board. I already replaced the control board, and the new board also shows 0 volts at Y, just like the old board did, so I am inclined to think that the board is not the problem.

The coil/relay contacter in the consenser housing is not hooked up, as I am replacing it with a new one. Even so, I don't see how it not being hooked up would limit the Y voltage to 0 on the control board. But I am a total rube in this area, and could be 180 wrong.

Grady White
Jun 14, 2013, 05:21 PM
If the thermostat is set for cooling & set below room temperature, you should have 24 volts ac between Y & C on the board. If you do not, remove the thermostat & jumper R & Y then check the voltage again. If you now have voltage, the thermostat is the problem.

J Russell
Jun 14, 2013, 07:38 PM
I jumpered R & Y at the thermostat and had no voltage. As the thermostat tested good, do I have any possible options besides the control board?

Grady White
Jun 15, 2013, 06:21 PM
You could have a broken wire between the board & thermostat. To check, set your meter for continuity, jumper R & Y at the stat, disconnect R & Y from the board, & test for continuity between R & Y. No contiuity means a broken wire.