Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Heater Control Valve: Description and Operation

The heater control valve is actuated by the air inlet door vacuum circuit (manual climate control) or the heater control valve vacuum control circuit (EATC). When the heater control valve is closed (full vacuum), coolant flow through the heater core is shut off and A/C cooling efficiency is increased.