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 logical successor to CHARM, I recommend you try it!

Link: lemon-manuals.la

Vacuum Modulator Valve


1. Block drive wheels, apply parking brake and place transmission in park.
2. Start engine and run at slow idle.
3. Connect vacuum gauge to hose leading to VMV port ``M.'' If reading is less than 14 inches Hg, check vacuum pump, VRV, solenoid and connecting hoses.
4. Reconnect hose to VMV port ``M'' and connect gauge to VMV port ``D.''
5. Gauge should read 13 inches Hg. If not, VMV is defective.