Need Air Conditioner Electrical Repair Advice
Hi everyone!
My problem is the compressor in our apartment AC won't activate. I believe the issue is electrical.
I have 2 questions:
AC NOTES:
I'm suspecting the issue is either:
So I'm thinking it's likely the thermostat/contactor unit, or something else electrical. NO IDEA how to repair a mechanical thermostat or contactor, and I can't even remove the thing. Any advice on how to remove the contactor, or other ideas on what else may be causing my problem (or any advice at all) would be appreciated.
My problem is the compressor in our apartment AC won't activate. I believe the issue is electrical.
I have 2 questions:
- How do you replace/remove this old contactor/thermostat unit (see photos)?
- See my notes below. If it's not the contactor/thermostat, maybe it's the condenser terminal wires? What do you think?
AC NOTES:
- Fan/motors work fine. But compressor won't turn on.
- The unit is a very old completely analog combination heating/cooling unit. Early 80's I think. Don't know what the model is (and couldn't figure it out), but the label says "McQuay Incremental Conditioner". Can't find a repair manual. Looks similar to this:
- It SEEMS the contactor/thermostat is a shared unit. There is a copper thermistor bulb that connects to the area behind the contactor (which I believe is the thermostat). In image 1 (front view), in the exact center of that unit you see a thin vertical cylinder; that's connected to the temperature dial above the c/t unit. When I turn that dial to the right (cooler setting), the metal "platform" in the center of the unit rises upwards, and when I turn the dial to the left (warmer setting) that platform lowers.
- Condenser/evap coils evaporator coils are clean. Both capacitors are tested.
- I SUSPECT there's an issue with the contactor/thermostat unit. When I press it down, it sticks down a bit. There are 3 leads; one on the left (A), and 2 on the right (one behind (B) and one in front (C)). When the plunger is up/open, A&B produce intermittent continuity. When the plunger is down, B&C produce intermittent continuity.
- Since I didn't know how to remove the contactor, I cleaned the exposed plunger coil with a toothbrush. Seems to not stick now when I press it down (but I think I damaged it when I cleaned it, see below).
- Prior to my first repair, you could sometimes "force" the compressor on my turning the temperature dial a bit towards warmer until you hear a click (which I guess is supposed to be compressor-off), then turn the dial a bit towards cooler until you hear a click, and SOMETIMES the compressor would activate.
- But after my "repairs" above, this trick no longer works. In fact, while the unit is on, I used a stick to manually press down on the contactor plunger, and the compressor STILL won't turn on.
- This AC is also our source of heat in the winter, and now the heating-mode won't work either.
- FRONT VIEW. Took off front plastic (not pictured). Right above the contactor is the temperature-control dial (not pictured). The box the contactor is in seems to be shared with the temperature controls.
- SIDE-ISH VIEW. Seems to be a couple of plastic holding clasps on both sides, but the unit won't budge when I push.
- BOTTOM VIEW. I removed a metal cover (not pictured) to expose the gold-screw at the rear. Looks like a previous tech put an arrow on it. I didn't try turning this screw, as I don't know what it is and worried the temperature control assembly may come apart (and I don't think I can put it back together).
I'm suspecting the issue is either:
- The thermostat/contactor unit. Thinking my issue is likely one of those components inside the unit, as the contactor isn't contacting anymore. I'm nervous about removing it because there seems to be gears and springs inside and if anything falls out of place I have no reference to put it back together.
- Burned condenser terminals. Although this wouldn't explain why the contactor is no-longer contacting right?
- Blown fuse somewhere. Haven't seen any fuses; will dig deeper into the unit tomorrow. But again, a blown condenser fuse wouldn't explain why the contactor is no-longer contacting right?
So I'm thinking it's likely the thermostat/contactor unit, or something else electrical. NO IDEA how to repair a mechanical thermostat or contactor, and I can't even remove the thing. Any advice on how to remove the contactor, or other ideas on what else may be causing my problem (or any advice at all) would be appreciated.
