Switch closest to O ring is Lamda rich mixture trip. Should be closed when water is cold. I believe switch closest to pump is idle motor ECU fast idle trip (don't have one of those). Ask someone with intact idle speed system to put an ice pick light on terminals 8 & 9 of ECU to tell if open or closed cold. Note water temp gauge sender is in block itself, just a bit closer to rear of engine. Bill Robertson #5939 >--- In dmcnews@xxxxxxxxxxxxxxx, id <ionicdesign@xxxx> wrote: > There are 3 sensors attached to the water pipe under the intake and before i put the engine back together i want to make sure these sensors are operating correctly so how do i test each sensor to make sure it is operating correctly? I have a new vacuum sensor so i just need to know how to test the other 2 electric sensors. > > Mark > 6683