Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Function Control Knob
The function control knob actuates a vacuum selector valve, which directs vacuum to open and close vacuum motor-controlled doors. With knob in NORM A/C, VENT, FLOOR, MIX or DEF (defrost symbol) position, outside air is drawn into system by the blower. With knob in OFF or MAX A/C position, the outside/recirculation door is positioned so outside air cannot pass into evaporator case. See Figure. Blower Switch
Blower speeds are controlled by 4-position blower switch and resistor assembly located in evaporator case, upstream from evaporator core. The blower switch can be set at LO, intermediate (2 positions) or HI blower speed. See Figure. The blower is turned off whe n function control knob is in OFF position.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.