how to troubleshoot three phase ac compressor?

Question

compressor will no run

Answer 1

first thing is to check the power with a multi meter and make sure you have 240 volts power...next make sure the contactor that turns compressor on is good....if the contactor closes make sure you have the correct voltage on the load side of the contactor....turn power off and check the ohms between any 2 lines of the compressor ...also check for ohms to ground from any line.....should be no reading to ground and every lead from compressor should read the exact amount of ohms between any two leads....if all of this checks good your compressor should run....does it humm when the power is turned on and is the contactor operating....if contactor not operating possible problems are 1 bad contactor coil..2 high pressure switch might need to be reset(red button where the freon lines come out of unit if it has one..3 low pressure freon switch might have it locked out...4 broke thermostat wires coming to outside unit 5 bad thermostat..6 bad transformer(will anything on the ac systme come and run...

Answer 2

Three Phase Compressor

Answer 3

check for a blowen fuze in the breaker box, one line fuze could be out, check the lines feeding the motor with a volt meter, across each set, then to ground,

Answer 4

William gives you a good place to start.
Also check the motor start capacitor and the tank pressure switch.