The short answer
A breaker that trips is protecting the wiring from something pulling too much current. The usual causes are compressor start components, a condenser fan motor that is dragging, or damaged wiring at the disconnect.
What you can check yourself
- Reset the breaker once. If it trips again, leave it off.
- Do not keep resetting it, and do not run the unit while it is tripping.
- Look for anything obvious outside: a chewed whip, standing water, a fan that cannot spin.
What gets checked first
- Compressor start components
- Condenser fan motor
- Wiring at the disconnect and the whip
Repair or replace?
Repair if it is a component. A shorted compressor is a replacement conversation.
When to call now
A breaker that trips again as soon as it is reset means leave it off and call.