no AC in July, what fun
 

it's a rheem heat pump, copeland scroll compressor

had an issue two weeks ago, seemed to be worn contactor, replaced it, things seemed ok for a couple of days

next replaced thermostat, old mercury switch type for digital, again seemed to have helped but compressor just worked inconsistantly

tonight it just will not stay on, it's almost midnight and it's hot

checked stuff with voltmeter as some other threads suggested, but can't
make sense of it

what readings should be where?

any help appreciated:confused:

couldn't find 24V anywhere, 18-19V at a few spots and 4-5V at others

transformer?

when contactor manually pushed in, compressor seems to run OK, but contactor won't stay drawn-in, fan runs constantly

check the voltage AT the transformer. If you have 24VAC on the secondary side of the transformer then you might have a bad T-stat or a bad low voltage wire. If no 24VAC at the transformer, then you just got real luck, just make sure to replace w/like rated transformer.
You may run into a universal transformer just be sure to wire it up for 120VAC on the primary side.

Thanks Kok328, I'm a semi-literate fool when it comes to AC/electrical, the only stuff I've learned is from trial&error and phone calls to friends of friends in the business

is the transformer in the air handler(inside) or condenser(outside)?

Hey no problem, it's called learning. I didn't know any of this at a point in my life and never took any formal or informal training. It will be in the air handler end. The best way to find it, would to trace the low voltage wires usually, thin wires in a brown casing. Working backwards, they will go from the condensor unit to the T-stat and then terminate in the air handler at a terminal strip. This terminal strip is powered by the transformer. It's job is to reduce 120VAC to 24VAC. If it goes bad you won't be getting 24VAC anymore and of course if it is not getting 120VAC then you won't get 24VAC with means the problem is not the transformer but further upstream.

had an AC tech friend stop by, turned out to be delay relay on outside unit

the old mercury switch therm required it

with the new therm it's built in, so he bypassed the outside delay, done

she's cooling down from 91 now, we'll see what happens when it gets to 74

thanks a "ton" for replying kok328, I'll probably be back one day, hopefully for something different