Operation CHARM: Car repair manuals for everyone.

Thermostatic Air Cleaner: Description and Operation

Fig. 10 TCA system:







The TCA system, Fig. 10, is mounted in the air cleaner assembly. It consists of a vacuum motor, hot air control (damper) valve and an inlet air temperature compensator valve. When the engine is not operating, no vacuum is present at either the inlet air temperature compensator valve or the vacuum motor. This allows the vacuum motor spring to close off the hot air passage from the hot air duct. When the engine is cold started, the inlet air temperature compensator valve operates to deliver the maximum vacuum to the vacuum motor. This completely opens the hot air control valve, closing the ambient air passage through the snorkel and opening the hot air duct. If engine speed is increased rapidly in this mode, system vacuum will decrease, allowing diaphragm spring to overcome the vacuum force and push the hot air control valve closed. Under normal engine operating conditions, the inlet air temperature compensator valve closes the passage from the intake manifold to the vacuum motor and opens the passage from the air cleaner to the vacuum motor. As fresh air is fed to the vacuum motor, the diaphragm spring forces the air control valve to close the hot air duct while at the same time opening the ambient air passage through the snorkel.