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

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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A/C Signal: Description and Operation

This signal is sent from the A/C amplifier. When the A/C clutch is energized the A/C amplifier will pull a signal line low that is in series with the A/C vacuum switching valve solenoid. The ECM uses this signal to adjust air/fuel mixture for the lean condition that the A/C VSV solenoid creates. The vehicles engine speed will be increased slightly to prevent stalling.