Can’t get the AC to turn on at all

hvac

Recently our AC stopped working. The thermostat is working properly, but the unit just started blowing hot air. I've never worked on a AC before, but I was trying to save some money. Anyway:

I started with replacing the capacitor on the unit, after completing that I turned the power back on but still nothing. I pushed the plastic piece in on the contactor and the unit came on, to include the fan. Once I released it the system shut off again. I went inside and checked the breaker box and noticed that two fuses had blown, replaced them and went back outside to see if the unit was running and it was for about a minute then it stopped. Fuses had blown again.

I asked a guy at the AC parts place and he said it could be the fan motor, but he also said it may be the contactor. I replaced the capacitor, fan motor and contactor. The new fan motor had 4 wires and the old had three. Brown, brown/white, black and yellow wires. Instead of using a dual capacitor for the brown and brown/white wires I just capped the brown/white, attached the brown to the F on the three prong capacitor I installed earlier and connect the yellow to the C and the black the line 1 on the contactor.

I made sure everything was secured and all plugged in. Everything looked good and I replaced the fuses in the interior breaker box. Turned the main power on outside, but nothing, fuses did not blow on the inside and thermostat was still working inside. I can't figure it out. Any ideas?

Best Answer

Sounds like a blown compressor.

Bad contacters don't usually pop fuses. And if it was simply the fan not coming on, the compressor should trip its own over-heat, not your breakers (unless it's old and grumpy: same prognosis; dead compressor).

If I were to keep trying to fix at that unit, the first thing I would do is install a "fused" (circuit breaker) disconnect for the condenser outside and a convenience outlet (both are now required by code).

That's step one of installing another unit, so it's no big loss if that doesn't help the diagnostics.

Air Conditioner Not Cooling : Tripping Breaker And Blowing Fuses –YouTube

My suspicion is we've got a bad compressor. Let me go grab my multimeter and get this thing tested out. Again, I'm going to go ahead and discharge the capacitor and then pull all the leads off the compressor. Then I'm going to go ahead and leave the fan motor connected and test. If this doesn't blow the breaker then that means our compressor's bad and it's time for either a new compressor or as old as this unit is, it may just be time for a whole new unit.

... It is as I suspected; the compressor's got a short in it. We're going to need either a new compressor or a whole new condenser unit. If I wanted to, I can recycle the fan top, the fan motor, and fan blades. That's a little bit more advanced troubleshooting and proving that it's actually our compressor that is down. We can replace the compressor if it's a clean change out. On this one, I think it's probably just maybe time for a new unit.

I've replaced compressors on commercial units (whose construction is conducive to such); it's not a very common practice for split systems, because that's the same amount of work, and you'd still have old equipment throughout.

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