Today I woke to no power to thermostst. Through this site I found out about the transformer. Check power to transformer good 120volts each wire. But no voltage out. Replaced transformer. Wired red to red and white to white incoming power. And blut to black blue and red to black red out coming. Still power to transformer no voltage out. Is there a chance the new transformer bad or is the voltage to low to read-used a 0.1-600volt meter and no reding on output. Tred each wire to ground tried wire to wire nothing. Is power out DC?? :confused:

With no wires connected other than line voltage to the transformer, you should have 24 volts across the low voltage load side of it...

If you check voltage going in to the transformer you should have 240 (give or take) If you do then the other side of the transformer should givr you 24 volts. It is very unlikely that your new transformer was bad when you got it but if you have a high voltage short you could have fried the new one as well. If you did the transformer should have gotten warn to the touch and you should be able to smell a burnt smell from it. It is best find the cause of why the old went bad. Remove all low voltage from the transformer and test the leads first.to be sure you have 24 volts coming out.

120 volts each wire... heat pump system? Was the thermostat switched to "OFF", or set to an operating mode, when you powered the system back up?

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Originally Posted by Joshdta

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I'm practicing! You got a problem with that?:p