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

Engine Speed Switch: Testing and Inspection




1. Connect voltmeter to green/white and black/white wires of electrical connector.
2. Increase engine speed to 2000 RPM, then slowly decrease engine speed and record engine speed at which current flows to circuit, which should be 1400 to 1600 RPM.
3. Slowly increase engine speed and record engine speed at which current does not flow to circuit
4. If difference of two recorded engine speeds is not 50 to 250 RPM, replace engine speed unit.