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sjc41, contractor
Category: HVAC
Satisfied Customers: 2062
Experience:  install and convertions for natural gas and propane gas- 25 yrs experience
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Air conditioner making a loud noise when starting.

Customer Question

Air conditioner is making a loud clunky noise for a couple seconds when it first starts up after sitting for a day or more. It didn't used to make such a loud noise on start up.

It's about six years old. It works fine once it gets going since I changed the circuit breaker from a 40 amp to a 50 amp. Is there anything I can do to help it?

Submitted: 8 years ago.
Category: HVAC
Expert:  sjc41 replied 8 years ago.

Hi and thanks for using

I'm assuming this is a whole house AC and you are referring to the outdoor compressor. Why did you change the breaker- was the unit tripping the 40?

Customer: replied 7 years ago.
this is a whole house AC with an outdoor unit. I had the breaker changed to a 50 amp because it was tripping, even with a new 40 amp circuit breaker.
Expert:  sjc41 replied 7 years ago.

Sounds like your compressor lost lubrication somehow, or got humid air in the line somehow, and is starting to seize up when left to sit. You should not apply 50 amps to 40 amp rated wiring. The clunk on startup sounds like the compressor shock isolators or mounts have loosened. If it is only 6 yrs old it should be under warranty.

Customer: replied 7 years ago.

The AC unit is not under warranty. I'm working with the developer on the proper wiring for the 50 amp. My question is if there is something I can do to help the AC unit, e.g., if lubrication is lost can I lubricate it?

How? Not likely humid air here in California, but if that's it is there something I can do? If something has loosened, can I check it and tighten it?

Expert:  sjc41 replied 7 years ago.

Lubrication is added along with the refrigerant. If you loose refrigerant you loose some lubricant. If the system is not vacuumed of air, water will be present .The volume and ratios types are stamped on the unit. You can read up on the subject online and you can get the gauges at harbor Freight for $60 bucks. They might have a vacuum pump and collection tank as well.

Most likely you will just fix it until it is broke. It is not rocket science, but you do need to know what you are doing. The fact that you subbed a 50A for a 40A is a clear indication you are out of your league. It will be less expensive for you to hire a licensed AC contractor, than to repair damage caused trying to fix it. Sorry to disappoint you, but I must be honest. Yes you can tighten loose mounting hardware.