Source of stray voltage?

Try removing the Defrost Circuit Board. I have found many times a defective CB can cause such strangeness.
If that doesn't help, disconnect all thermostat cables to Tstsat, Indoor & Outdoor then run a megohmeter between all wires. I would do that before buying a circuit board.

Thanks.

If you don't have the problem when you use the old stat by wiring it up at the outside unit. It tends to indicate that the problem is in the wires from the stat location.

beenthere said:

If you don't have the problem when you use the old stat by wiring it up at the outside unit. It tends to indicate that the problem is in the wires from the stat location.

Click to expand...

The thing about the wiring at the stat is that I kept the back plate of t-stat2 connected while "using" t-stat one at the heat pump.

At that point, I got normal readings both on the wires to the hp and normal readings on back plate-2. That is what has me stumped. If the wiring was faulty, wouldn't you expect to have the same problem?

I tried several wiring configurations: (hardwired wires at stat, wired r @ the a/h to y to the heat pump and kept the stat wires out of the circuit, and always there was voltage on the o wire). I never even thought about by-passing the defrost board on the heat pump.... Not only should I say thanks to Gene, but Thanks a lot:thumbup:.

Well, I left the o-wire as a temporary fix, but thanks to B.T. and Gene, I have some better ideas.

Sometimes. The wires in the wall can be shorting when the stat is on. but, when you remove the stat, it takes just enough pressure off the wires. that they no longer touch,

I am returning on Monday. Again, thanks for the input. I don't like to use anybody as a crutch, but it's nice to have someplace to go to when being stumped. Sometimes, the manufacturer tech guys, and local supply guys just aren't sure themselves.

Always learning..

I also forgot, sometimes a sub base will have a faulty diode allowing feedback. Not applicable in this case though.

Even us old guys get stumped sometimes. The factory techs are limited by diagnosing over the phone.

There is always something new to learn in this trade even on the older proven technologys. The new technology coming everyday presents even more challenges.

That's what I enjoy on forums like this. An exchange of ideas & solutions.