Description: An array of wiring, switches, relays and controls. These components may take on dual roles (both a sensor and a switch), where they turn on certain parts of the circuit based on operating conditions. Increasingly, these circuits and controls are integrated with the vehicle’s powertrain control module (PCM), even on cars without Automatic Temperature Control (ATC).
Purpose: To electrically manage the HVAC system, based on driver demands and vehicle operating conditions. Cars with Automatic Temperature Control (ATC) provide automatic control over HVAC circuits.
Maintenance Tips/Suggestions: Proper HVAC operation requires normal operation of all parts of the control circuits. As an example, a failed temperature switch may cause faulty erratic or no compressor operation, affecting cooling. Problems with HVAC switches and electrical circuits may cause no cooling, poor cooling, excessive cooling, or erratic temperature control. To determine the root cause, have the A/C system looked at by a professional technician.