dumb question.......likely simple answer

[KEVIN MUNCASTER]

....was changing intakes and noticed a 2 prong sending unit next to my vacumn pump at pass. rear of block on top. Sender is not hooked up, and everything on my truck seems to work fine. I can't even find the wires that should be there. What is it for ? I could look it up but thought I'd ask.
I know the thermal fast idle switch is on the side of the motor, but this is on top.

Hmmm ?

Kev :D

[john8662]

Sounds like your glow plug inhibit switch has been removed. My 86 has the inhibit switch on the pass side head on the head block off plate. Does your engine have just a smooth block off plate on that side, or a plate with a pipe plug in it now?

[diesel65]

That is the thermal cutoff switch for the glow plug controller.
Depending if it was replaced it might not be temperature sensitive (lack of a better word), GM had a bulletin for warm engine hard start, the fix was you needed a glow cycle but that sensor wouldn't allow the controller to cycle, so GM made a dummy sensor that has a shorting bar inside and allows the controller to cycle on a warm engine.
On your vehicle someone could have jumped the connector and tucked the wire away with electrical tape.

[KEVIN MUNCASTER]

I guess my mian concern is: If left alone, is it ok ? My glow plugs will cycle a couple times after start up, more so in cold temps.

I found a note in the original owner's service log that said he had bypassed the glow plug contoller and there were 2 new ones behind the seat when I bought the truck. I could see where there had been a switch mounted on the dash, but it was no longer there. I looked and saw that the controller was in fact hooked up and working. I guess he had a change of heart.
:confused:

[john8662]

With the inhibit switch missing you'll see better starting hot, the glow system will be used more. All the switch does it keep the glow plugs from cycling every time you start the engine. I know on my 86, I see the plugs on in the morning, and usually not at all the rest of the day (hot day). In the winter, I get to glare at the light a little more.