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Discussion Starter #1
Went to start up my truck this morning and it would not start. I pressed the "Charge Protect" on the AIC and the battery volts stayed at 12v. I know when the relay engages, the voltage drops down to 10.9-11.0. The WTS light operates as it should.

I swapped out the GPR and it still does the same. GPs are new. Checked the UVCH and no burnt pins.

I had to jump out the big terminals to get my truck started.

Anyone have a schematic of the GPR wiring? I know the ECM controls the ground side of the coil of the GPR. Any particular place to look for any issues?

Thanks

Billy T.
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Hit "G" on the search key and scroll down to glow plug relay.
 

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The switched 12V+ side (red wire) is on the same wire that supplies voltage to the fuel filter heater element. The two are tied together in the engine harness near the connector for the fuel bowl harness. If you pulled voltage from that wire upstream of the engine (connector at fuse box) then you're not getting voltage at the relay. Check with a multi-meter for voltage on the red wire when the key is in the run position. Should be hot at all times while the key is in "run". If voltage is present, then check the opposite wire (purple) for ground when the key is initially turned on.
 

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Discussion Starter #5
I have 12v+ on the red wire. I have to use a jumper to ground the coil of the relay. Once grounded, I heard the relay close.

It started to snow here and my troubleshooting stopped until I can my truck inside my shop.

Billy T.
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