Hey guys I could really use some advice. I have a spilt unit hvac system. the unit on the roof has a power supply from 120v to 35vdc and 12 vdc which goes into the indoor unit. my problem is when I plug the dc voltage out to the indoor unit I no longer get a steady dc voltage reading. if I unplug it the dc out remains constant. Any ideas?

indoor unit disconnected I read 12vdc to common and 35vdc to common
indoor unit hooked up. do not get any accurate reading. just jumps around

This unit is 120v 60hz

 

From the information given, I'd say the supplies are either overloaded or defective.

 

From the information given, I'd say the supplies are either overloaded or defective.

That is what I was thinking as well, but they replaced the power supply boards with part for part replacements