Compressor runs for only a moment the circuit breaker trips

30 amp and yes lights dim 30 amp and yes lights dim

I'd be looking at replacing the compressor start capacitor. The capacitor supplies a high voltage "Kick start" to get compressor going. If you give me your model number off bottom of upper (roof) unit, I can get you a part number. Be Real Careful with capacitors, they can give a real dangerous, if not fatal shock of 300-400 volts, even when power is turned off !! If not experienced in that area, get back to me for instructions, or ask someone who is experienced to perform the job. New Capacitors run,$20-$40. and take about 20-30 min to change. I'd be looking at replacing the compressor start capacitor. The capacitor supplies a high voltage "Kick start" to get compressor going. If you give me your model number off bottom of upper (roof) unit, I can get you a part number. Be Real Careful with capacitors, they can give a real dangerous, if not fatal shock of 300-400 volts, even when power is turned off !! If not experienced in that area, get back to me for instructions, or ask someone who is experienced to perform the job. New Capacitors run,$20-$40. and take about 20-30 min to change.