Preliminary Information - HVAC System - Automatic

Temperature control problems can be traced to the refrigerant system, electrical wiring or vacuum connections, mechanical problems (i.e. sticking valves), and/or the heater A/C control functional test.

Inspect
^ Refrigerant, vacuum or mechanical systems.
^ Blower controls.
^ Compressor controls.
^ Air delivery and temperature controls, including diagnostic procedure for the heater A/C control microprocessor.