Contactor
The relay that sends line voltage to the compressor and outdoor fan.
AC Breaker Keeps Tripping: How to Find Out Why
How to diagnose an air conditioner or heat pump that keeps tripping its breaker: a grounded compressor, a locked rotor, a shorted fan motor, wiring faults, high head pressure or a weak breaker.
Replacing a Run Capacitor or Contactor: How to Pick the Right Part
How to choose a replacement run capacitor (µF, voltage, dual vs. single, size) and contactor (coil voltage, poles, amp rating), with the common mistakes that bring callbacks.
AC Compressor Not Starting: Humming, Clicking or Nothing at All
Diagnose a compressor that won't start by what it does: humming points to capacitor or locked rotor, clicking to overload, silence to the control circuit.
AC Not Cooling? A Step-by-Step Diagnostic Checklist for Techs
Work an AC no-cool call in the right order, from the thermostat call to airflow, electrical and refrigerant charge, without guessing.
Condenser Fan Not Spinning: Capacitor, Motor or Control?
Find out why an outdoor condenser fan won't run, from the fan capacitor and seized bearings to the contactor, wiring and heat pump defrost.
How to Test an AC Contactor: Coil, Contacts and Voltage Drop
Test a condenser contactor the right way, from 24 V at the coil and coil resistance to pitted contacts and voltage drop under load.