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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Engine Speed Signal

Engine Speed Signal

The Air Conditioning Control Module (A/CCM) receives an engine speed signal from the Engine Control Module (ECM).

This signal facilitates compressor lock sensing (12 cyl. vehicles only).

This signal also aids the A/CCM inhibition of the heated screen relays. At engine speeds lower than 800 RPM the A/CCM assumes poor idle or engine not running and will not permit the selection of the heated screens.