I have a rather old central ac unit. It wasn't working at all and it
looked like the contactor was bad. I replaced the contactor and the
unit started right up. It will run for about 45 minutes and cools
fine. Then it trips the breaker. It cools fine while it is running.
The compressor already has a hard start kit on it. I have a couple of
How can I determine weather the condenser fan or the compressor is
causing the breaker to trip?
Will a dirty condenser /debris or refrigerant charge contribute to the
What should I check from here?
Thanks for any help
A similar thing happened to me. My son's neighbor, a midnight A/C
technician, diagnosed the problem in a nonce.
CAREFULLY put a finger on the breaker (side of the breaker is best). If the
breaker's warm, replace it.
$15 at the box store and everything is cool.
When ever I'm working on mine I also clean out the debris.
I'd start by replacing the breaker. They get weak with age and
multiple trips. Then they trip at less than the rated current. I'd
also check and tighten ALL the connections between the breaker and the
The fan motor is typically a small fraction of the current draw. The
compressor is the bulk of it.
A low charge can cause problems. If it cools ok when running then
it's probably fine. I assume you don't have gauges. The old school
technique is the big copper pipe, which is the return, should feel
like a beer can just out the fridge where it goes into the outside
unit after it's been running for a little while.
Many good suggestions already made. Also make sure that the condenser fan is
always running when the compressor is. If the fan stops on internal
overload, the head pressure will soar and the compressor will also go out on
You already got some suggestions on possible problems, but I have another
route you may want to consider.
If that AC is very old, you may be able to replace it and save enough on
the electric bill to pay for most or all of it. Start thinking about it
while the AC is still running and you can take the time to get what you
really need at a good price. Maybe a fall or winter job rather than the
first hot day of next summer when prices will be higher.
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