Depends on the year I think. My 82's switch is in the very back of the passenger head, and its a PITA to get to. I couldn't even find one so I took the power wire running to the switch, ran it back to the cab through a toggle, then back to the other prong on the plug to feed power to the solenoid. NOTE: the power will feed the solenoid for increased idle AND injection advance. (Should be the other green wire). The coolant temp sensor is supposed to shut off around 85 deg F, running that much additional advance with a fully warmed up engine is probably not a good idea. However, if you disconnect the green wire going to the injection pump and just leave the one on the solenoid, you have a handy high idle on command. If your injection advance is working you'll notice a definate change in the rattle when it is engaged.