My landlord recently hired someone to install a common wire from my Goodman AC unit on the roof down to where the thermostat is. The current thermostat works fine, but is non programmable and battery powered. My landlord got an ecobee 3 lite to replace it but when I began to install it, I noticed the voltages on the wires were kinda off. R to G is 14.7 Vac but C to G is 59.7 Vac when the ac fan is running and 53 Vac when it is off! Did the handyman screw up installing the C wire or is there something wrong with the transformer on the AC unit?

  • What's R to C measure like? – ThreePhaseEel Jul 9 '19 at 0:24
  • 39 Vac with the fan on and off – Nick Jul 9 '19 at 0:29
  • actually 36 and dropping with the fan off, it seems that the C voltage drops with time when the ac fan turns off – Nick Jul 9 '19 at 0:30
  • 2
    You're a tenant. That's a big bag of "Not Your Problem". I'd stop futzing with it before you get blamed for anything that is wrong... – Harper - Reinstate Monica Jul 9 '19 at 1:07
  • "when I began to install it, [instead I stopped and decided to check voltages across wires that should be dead because the system should be off]". After you install it and it burns out, then we can play the blame game. For which we'd need pictures of all the terminals at both ends. 39vac is nominal. – Mazura Jul 9 '19 at 1:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.