Ok well I just found your forum and browsed your past posts. Here is what I have. 1988 c3500 with 6.2. When I turn the key on the glow plug indicator does not come on. I tested the connections at relay and on the outer terminal I have 11.98 volts and the inner terminal I have 0. I ran a jumper cable from bat to the side with 0 and the glow plug indicator on the dash came on and I put a meter on one of the glow plug terminals and i had 11.98 volts at the glow plug. So after reading old posts from this site i went and bought a new relay. $80.25 later I installed it and still have same problem!!! Where do I go next? Any suggestions?

Ok well I just found your forum and browsed your past posts. Here is what I have. 1988 c3500 with 6.2. When I turn the key on the glow plug indicator does not come on. I tested the connections at relay and on the outer terminal I have 11.98 volts and the inner terminal I have 0. I ran a jumper cable from bat to the side with 0 and the glow plug indicator on the dash came on and I put a meter on one of the glow plug terminals and i had 11.98 volts at the glow plug. So after reading old posts from this site i went and bought a new relay. $80.25 later I installed it and still have same problem!!! Where do I go next? Any suggestions?

There's a little glow plug inhibitor switch screwed into one of the coolant passages. Sometimes in one of the heads and sometimes in the coolant manifold. Has two prongs. It is supposed to stop the glow plugs from working once the engine is warm. If it goes bad, they never work. Just unplug and connect the two wires together. You can also buy a new switch for $10, but it's not needed. Just bypass it.

Ok, on the back of the passenger side head I found what looks like what you describe and has two prongs. I disconnected it and ran a jumper wire from one to the other terminal, bypassing the switch, when I do that i hear a clicking sound from the injector pump but still no glow plug light. Grrr......

Make sure you have a good ground on your wiring harness or the relay won't work.

ok so that sensor on the back passenger head of my 82 only has one prong and one wire?

And where is the ground at on the wiring harness?

I think my controller may be bad... when the engine is warm the glow plug light will not come on... What do you guys think? Just replaced the relay by the way

I think my controller may be bad... when the engine is warm the glow plug light will not come on... What do you guys think? Just replaced the relay by the way

They are not supposed to come on when the engine is warm; that's what the inhibitor switch is for. A '82 should have a different system than an '88, btw.


Twilkins, if you have a chance to return the glow plug controller, you could just wire it up for manual operation with a Ford starter solenoid ($10) and spend the $80 on a set of new G60 glow plugs instead ...

well i have the manual switch... its just wired in weird i guess... and my truck will not start at all with out hitting the glow plugs with some juice for a couple seconds... but now they wont come on at all... despite the new relay, will the controller cause this? ive never had any problems before

turns out it was just that pink and black 20g wire just needed to be grounded... thanks for your help guys

BTW, that 2 prong temp switch is for the operation of the cold advance solenoid and the fast idle solenoid. Its in the circuit to prevent operation of those 2 items when the engine is warm.:)