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

Low Temperature Vacuum Signal Modulator

This unit is located at the left side of the front upper crossmember, just ahead of the radiator, on the same mounting bracket as the TCS ambient temperature override switch and is connected to the EGR vacuum signal hose. The modulator is open when ambient temperatures are below 60° F. This causes a weakened vacuum signal to the EGR valve and a resultant decrease in the amount of exhaust gas being recirculated.