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.
Thermostatic Air Control System: Operation
Air intake of air cleaner is connected to fresh outside air and to pre-heated air through a snorkel connected to a shroud over the exhaust manifold. A vacuum motor controlled flap allows fresh air, pre-heated air, or a combination of both to enter air cleaner housing as needed. An ambient temperature sensitive vacuum switch, located in air cleaner housing, is used to control manifold vacuum to vacuum motor which moves the flap. See Fig 1 .
At ambient temperatures of less than 75°F (24°C), temperature vacuum switch will allow vacuum to reach vacuum motor and air flap will allow pre-heated air to enter air cleaner housing. At ambient temperatures greater than 75°F (24°C), temperature vacuum switch will gradually leak vacuum into air cleaner housing which will cause vacuum motor and air flap to return to its normal position, allowing fresh outside air to enter air cleaner housing. Temperature sensitive vacuum switch will modulate amount of air flap opening, depending on ambient air temperature, to give a blend of fresh and pre-heated air as necessary.
Use the Manual With the Right Hardware
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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.