Testing Thermostatically Controlled Air Cleaner

With temperature in engine compartment at 85°F or less, engine cold, flap valve should be in up position shutting off cold air intake. If valve is not in up position, check for possible wear or breakage of valve in duct. If worn or broken, replace valve and duct assembly as they are not serviced separately. Remove assembly from vehicle and immerse in water making sure thermostatic bulb is completely covered. Raise water temperature to 85°F, allow five minutes to stabilize, flap valve should be in up position. Increase water temperature to 110 °F, allow five minutes to stabilize. Flap valve should now be in down position shutting off hot air intake. If valve does not meet these requirements, and no binding or damage is present, thermostatic valve should be replaced.