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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A/C Signal: Description and Operation

On models equipped with air conditioning, the A/C signal informs the ECM that the A/C switch is turned "ON" and the A/C pressure cycling switch is closed. With this input, the ECM will raise idle speed by means of the fast idle solenoid. This system prevents poor idle quality and possible stalling due to the extra load created by the A/C compressor.