Blower and A/C Controls (Manual)

Circuit Description

Blower control
With the ignition switch in ON, battery voltage is applied to the coil of the blower relay. With blower switch in any position except OFF, ground is provided to the coil of the blower relay through the blower switch. Battery voltage is then applied to the blower motor through the closed contacts of the blower relay. Ground is provided to the blower motor through blower resistor and blower switch for the desired blower motor speed.

As the blower switch is moved from OFF to position IIII, resistors in the resistor block are bypassed. Decreasing the resistance will increase the current applied to the blower motor. This increases the blower motor speed. When the fan switch is in position IIII, all of the resistors are bypassed. The maximum current is now applied to the blower motor so that it runs at the highest speed.

A/C control
With the ignition switch in ON and the blower switch in any position except OFF, the blower relay coil energizes and battery voltage is applied to the A/C switch through the closed contact of the blower relay and fuse 9. With the A/C switch ON, the engine control module (ECM) will ground the coil of the A/C control relay after a short delay to adjust idle speed. Battery voltage will then be applied to the compressor magnetic clutch from the A/C fuse through the closed contacts of the A/C relay. The A/C compressor then runs.