Carrier AC Compressor and Fan not starting

544 Views 10 Replies 4 Participants Last post by jhunolt, May 28, 2020

jhunolt

Discussion Starter · May 27, 2020

Hi All,

I have a Carrier 38CK-036-340 AC from 2001. A month or so ago I uncovered it and ran it for about 15 minutes with no issues, the temp then was in the upper 70's.

Yesterday we had the first day just short of 90 and today and tomorrow are expected to be over 100.

I turned the AC on yesterday and the in house fan started running but the compressor outside never started. I could hear a humming sound so I immediately turned things back off.

I took the cover off and the contactor is closing, that was most of the humming sound, but neither the fan or the compressor are starting. There is no dirt built up, fan turns freely. There is no obvious leakage from the capacitor.

My question is whether a bad contactor or capacitor, or even a bad compressor would also keep the fan from starting?

Given the costs I am thinking of ordering the contactor and capacitor and just replacing both.

Any insight appreciated.

Thanks,

Jon

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jhunolt

Discussion Starter · #5 · May 27, 2020

Thanks for replying surferdude2 and 57TinkerMan. I did check the AC breaker and it was not tripped and I turned it off an back on. The disconnect doesn't appear to have fuses, at least not in the removable part, it has a t-handled part you pull out and flip over to set to on and off. The disconnect is in a rather larger box mounted to the side of the house so I may need to turn the breakers off and remove the cover to see if it has fuses. I did notice the contactor seemed to spark when closing with the disconnect on.

I have a multimeter so I can check out the voltage and for any fuses.

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jhunolt

Discussion Starter · #7 · May 27, 2020

Hi All,

Some more info, there is 230 at the disconnect and there are no fuses, I also confirmed 230 at input and out put of contactor when I manually close contactor. I disconnected compressor wires from contactor. Hum was coming from fan so I tried pressing contactor and manually pushing fan, this worked and fan sluggishly started but got up to speed in maybe 10 secs. I reconnected the compressor wires and I still had to start the fan manually, but it would run once started.

I then repeated this all by turning AC on from the thermostat and manually starting the fan and I could get it started. I may not have left it running long enough to verify the compressor was running, but the air from the registers was not really cold.

I will try this again and see if I can check the temp of the smaller copper line.

I am thinking this sounds like the capacitor so far?

Jon

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jhunolt

Discussion Starter · #9 · May 27, 2020 (Edited)

A little more info, used thermostat to trip contactor, bump started fan, and checked return small copper line which did not get hot. After a couple of minutes though the fan speed dropped a bit for about 3 secs and it sounded like compressor may have been trying to start and unable.

Is the capacitor key to the compressor starting even if fan is already running?

Also the capacitor is a HC98$A046D 46/6 and Repair Clinic calls for a P291-4554RS 45/5, how much difference is there?

I only see the one large round capacitor, if it was a dual would there be another smaller one?

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jhunolt

Discussion Starter · #11 · May 28, 2020

Good news everyone!

Replacement cap from repair clinic arrived today, it was shorter and fatter, but electrically the same. Hooked it up and wire tied it in place for now and the AC is working fine.

I did notice that only the HERM terminal is labeled, so I just copied the wiring from the old one, same wires to the left and right of HERM.

Thanks to everyone that offered the benefit of their knowledge!

Jon

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