Any A/C experts?

[Andrew_K99]

Back in early July my A/C died. Being the DIY'er I am I did some searching to see if I could figure out what the cause was. On the outside unit I removed the cover and quickly discovered a wire that had corroded at the connector and came apart. Relieved this was an easy repair I could do I replaced the connector and everything was good again.

Two days ago our A/C died again! The unit is getting old and replacement is in the near future but I am hoping not this year. Once again I pulled the cover off and this time noticed that the connector that I had replaced had melted and was chared! Once again I have replaced the conector.

I am assuming this is just a band-aid repair and there is something else going on to cause this terminal to overheat.

The wire in question goes from the capacitor to the A/C coil power relay.

Anyone know what might be going on? Is there anything that should be relpaced (aside from the whole unit) to extend it's life?



AK

 

[DurocShark]

Replace the cap would be my guess.

 

[Andrew_K99]

Replace the cap would be my guess.

It was replaced last year, could it need replacement again?

 

[DurocShark]

Could. I can't see any other reason why you would be getting overvoltage on that line.

 

[PenMan1]

Replace the capacitor. Be VERY CAREFUL removing the leads from the cap. I'd wear thick rubber gloves and stand on a rubber mat. The capacitor carries huge voltage and if it is damaged (likely)it could arch from unexected places.

Additionally, work with one hand during this proceedure.

 

[t001xa22]

Andrew, what Andy said is dead on. The capacitor can hold a charge for a while after voltage is cut from it, and it can still discharge a nasty arc during this time. From what I can see, it seems to be maybe a start/run capacitor, serving two functions in one unit. Sometimes, when the unit is starting up, the start capacitor function does not kick out, and allow the run function to take over. If that happens, there will be a continuous over-voltage hitting the compressor. Also, if the compressor has not released some of its head pressure when it tries to cycle, the backpressure can put too much load on the electrical system, and that can overload spots like the terminals. Just offering a couple of cents worth.

 

[Andrew_K99]

Thanks for all the comments.

I think I am going to source a new capacitor and relay and replace them just to be safe. The unit is 15-18 years old and will hopefully last a little longer.

AK

 

[aplpickr]

Dual run cap

Your cap is a double-run. The center post is common with the condenser fan and the compressor. The low side (usually 5 mfd) is for the fan. The high side (usally ~30 mfd) is for the compressor. Which side is burning off? That will eliminate half of the failure possibilities. Start caps are black plastic, not grey metal. Bad run caps are usually swollen (not oval) or obviously bad. If you do not have a potential relay (not the contactor relay) then the compressor cap is always wired into the system. Whichever cap side is burning tends to show heat caused by problems with the motor or compressor. Bad bearings in either are a common cause. Improperly changed air filters CAUSE 90% of all compressor failures. If you can read a book thru a new filter, get something better. Setting the thermostat colder will not make it get colder any faster. Settings below 65°/68° cause compressor failures.

Retired HVAC mechanic

 

[Andrew_K99]

Your cap is a double-run. The center post is common with the condenser fan and the compressor. The low side (usually 5 mfd) is for the fan. The high side (usally ~30 mfd) is for the compressor. Which side is burning off? That will eliminate half of the failure possibilities. Start caps are black plastic, not grey metal. Bad run caps are usually swollen (not oval) or obviously bad. If you do not have a potential relay (not the contactor relay) then the compressor cap is always wired into the system. Whichever cap side is burning tends to show heat caused by problems with the motor or compressor. Bad bearings in either are a common cause. Improperly changed air filters CAUSE 90% of all compressor failures. If you can read a book thru a new filter, get something better. Setting the thermostat colder will not make it get colder any faster. Settings below 65°/68° cause compressor failures.

Retired HVAC mechanic

Thanks for the reply. It is the wire coming from the center terminal on the capacitor. Does this mean anything to you? Could this cap be different? I could take a picture and get more information on it. A huge thanks for the info!!