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)

Or, hide this message: temporarily or permanently

Air Injection: Testing and Inspection




1. Remove vacuum switch from vehicle.
2. Connect a hand vacuum pump and an ohmmeter to vacuum switch.
3. With 3.9 inches or less Hg vacuum applied, ohmmeter should indicate no continuity between switch terminals.
4. With more than 3.9 inches Hg vacuum applied, ohmmeter should indicate continuity between switch terminals.