Inspection of HVAC Control Module and Its Circuit: Notes
HVAC control unit and its circuits can be checked at HVAC control module wiring connector by measuring voltage.
CAUTION:
If you connect a voltmeter or an ohmmeter directly to the HVAC control module by disconnecting the HVAC control module connector, you can damage the HVAC control module. Never connect a voltmeter or an ohmmeter directly to any terminal on the HVAC control module by disconnecting the HVAC control module connector.