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Glow plug controller switch that runs controller?

9K views 12 replies 4 participants last post by  JMJNet 
#1 ·
Hey all
-started a new thread for my glow plug issue, SSD said that its likely the 'switch' that controls the glow plug controller-since new controller didn't fix.


Any thoughts? is that a GM part
 
#2 · (Edited)
If the controller and the GP's all test good, the "switch" Walt may be talking about is the Coolant Temp Switch in the front crossover pipe. That tells the controller if the engine temp is below or above 125F. Below; it triggers the controller to energize. Above; the GP's won't energize.

If you decide to replace the CTS, remove it and take it with you to make sure you get the right one. The parts store most likely will give you one for a '94 and up. They are not the same and will require a new connector also if you upgrade.

I put a manual GP override switch on my '93 for those a-little-too-hot starts on a high mileage engine. ~FH
 
#3 ·
#4 · (Edited)
Yep. I thought that was a bit low for a cut-off temp myself but I got that info from SSD.

A bypass for what? ~FH

ETA: Ooops! I overlooked your link. Just make sure your present GP's can handle the unregulated energize period. That mod you linked to specifies Delco 60g GPs.
 
#5 ·
IIRC, you can try to unplug the CTS and see if you can get the GP to work. It acts like it is -40 degrees.
 
#6 ·
you are saying pull the module harness from the glow plug control module and then try to start it?
 
#9 ·
FH..you said:
Yep. I thought that was a bit low for a cut-off temp myself but I got that info from SSD.

what are we talking about cutting off?? my glow plugs? guys say they come on 100% of the time.
 
#11 ·
As racer just said, and also according to Walt at SSD (and the living example of my '93 C3500), on the '93 if engine temp is above 125F the GP circuit will NOT be automatically energized. With high mileage and low compression the engine needs all the help it can get to start. Thus, the override switch mod.

My '93 has been sitting for awhile awaiting surgery but I just went out to start it and the GPs did NOT come on, even with the CTS/ECT wires disconnected. So a button or switch to enable/disable the coolant sensor may not be the best fix. I had to use the manual 12v solenoid override that I usually use when the engine is warm. ~FH
 
#10 ·
There are 3 different generations of the 6.5 and they all treat the glows slightly differently.

Yours is pre electronics and the ECT sensor controls on/off time.
94/95 OBD1 are controlled by the ecm from an ECT reference but cycle time is programmed.
96 + OBD II are also controlled by the ecm similar to OBD1

Besides the other thread you have running has a link to help you out from the faq on how to disable the ECT sensor with a toggle switch and manually trigger a glow cycle reguardless of engine temp,multiple threads for the same problem will only cloud the issue.
 
#12 ·
FH- You rocked it! Thanks guys
 
#13 · (Edited)
There is a quirk that after the battery is disconnected, the GP have some sort of amnesia. It will not turn on until the 2nd start or 3rd.

I am not sure if that happens to the 93 or not. It does it on mine.
 
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