magnetic contactor bad? Help!

Of course of all days, today my coolant pump goes out! Or maybe it is the magnetic contactor that is bad, how do you check them? How do I check the circuit breaker? The Bestact relay appears to be fine.

Symptoms:

The pump is spinning at maybe 1/4 the rpm as normal, and then it shuts off after about a minute. Sometimes the motor runs backwards. If I press the contactor in, it won't stay. After a while, maybe 15 minutes I can get the contactor to work, the motor spins, but again too slow, and sometimes backwards.

Sounds like the contactor is only providing two legs of power. Is that correct?

Is it the contactor that is going bad, or is is the circuit breaker? Or the motor? Help!

If you are trying to start up and run on only 2 phases, the motor will not start on its own. The only way you could get it to start is to manually spin it. You are tirpping the overloads when the motor doesn't get up to speed. It does sound like a phase is missing. Measure with a voltmeter between the wires going to the motor. I'm assuning this is a 480 volt motor. You should read between 420 and 480 volts between each lead. If one of them doen't read within this range, that is your cuplrit. I don't know your specific installation, but generally there is a breaker or set of fuses, and a set of overloads. If you have a problem with loading the motor or not getting up to speed or a partially shorted phase, the overloads will pop. If you have a completely or motsly shorted phase, the breaker or fuses will pop. I hope this helps.