Glow Plug Relay - Diesel Truck Forum -
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post #1 of 5 (permalink) Old 03-21-2006, 06:26 PM Thread Starter
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Glow Plug Relay

Why does this happen? Over the last couple of years Iíve replaced 3 GPRís. Iíve noticed that on the new ones, both of the big posts are copper colored and shiny. As time goes by, one of the posts will fade and eventually tarnish &/or corrode. By the time the relay goes out, one post looks like itís a 100 years old and the other one is still pretty new looking. Also, the last 3 times the GPR went out it was b/c the ďtarnishedĒ post came out of the base. It kind of looks like it arcíd on the inside of the relay and the post blew out of the unit.

The parts store I go to happens to have some pretty knowledgeable guys. I asked why my GPRís are only lasting 10 Ė 12 months on average. He said it sounded like Iíve got a grounding problem and to check the glow plugs and the wire harnesses. I just said Ok and finished the transaction. I didnít tell him that all 4 wire harnesses and all 8 GPís are only a bout a year old.

Iíve always used the Motorcraft brand for GPís, GPRís, and wire harnesses. So I donít think quality is an issue, but maybe it is.

So my main question isÖ Why does one post on the GPR always degrade?

My other question isÖ.. Am I missing something? Should I look further into his idea of a grounding problem? What else needs to be grounded?

OR, is all this just typical of the Motorcraft relay?

Thanks for any light you can shed on this for me.
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post #2 of 5 (permalink) Old 03-22-2006, 01:27 AM
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GPR relays

He there neighbor let me give your question a try.

First yah know the parts are copper and they are subjected to the elements and the color you describe is normal. One being darker is due to the current load that it may be carrying.

I've read in the other forum you know the one where bickering is a one of the guiys gave me a list of part numbers and NAPA has a heavy duty read higher current rating then the OEM's. The one sticking point is that it's not a physical fit as the OEM but can work and will last.

Here it is below:GPR
F81Z-12B533-AC $76.02
Carquest #RY-175
International #1831646C1 ~$30
International #1826634C94. $53.83 (for a í96?)

Let us know how yah made out....C-man
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post #3 of 5 (permalink) Old 03-22-2006, 01:59 AM
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what happens is internally the mechanism that actuates to engage the relay atrophies and doesn't make good contact anymore resulting in arcing which further weakens the GPR. The arcing generates excess heat which causes the plastic housing to get brittle and break. The discoloration is similar to what happens when you arc anything you'll see an area of discoloration around the center of the arc your stud happens to be that point.

The OE GPR is not really up to the task especially if you're in a cold environment. The early trucks like yours & mine have a computer glow plug logic that automatically engages them regardless of the temperature so we see quite a few failures. The answer to the problem is a 2 part soloution 1 a chip with better glow plug logic or reflash stock PCM to a TDE family code.

the second part is to replace the stock glow plug relay with a DC contactor rated for well in excess of what the system will actually use. Link to a vendor that sells them. It's more expensive than some of the aftermarket GPR's but I think it's worth it.

The contactor will bolt into the same place as your factory GPR no changes in wiring only some slighty pulling of the wires may be required if you don't have enough slack. Mine with the pigtail end had plenty of slack. It will even fit under the removeable cover if you still have it on your engine.

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post #4 of 5 (permalink) Old 03-22-2006, 02:17 AM
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Originally Posted by BJS

the second part is to replace the stock glow plug relay with a DC contactor rated for well in excess of what the system will actually use. Link to a vendor that sells them. It's more expensive than some of the aftermarket GPR's but I think it's worth it.

Nice post!!! Thanks!!!:thanks:

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post #5 of 5 (permalink) Old 03-22-2006, 06:24 PM Thread Starter
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Thanks for the replies. I kind of figured teh discoloration was due to the load going thru that particular post. It's actually the discolored post that get's blown out. I guess this tells me I need to upgrade to the stancor GPR. I've seen that one cussed & discussed before. But I never think about ordering one until I need one. By the time that happens... I really NEED it and can't wait. It alwasy happens to be cold whether when the gpr goes out on me. The price on the link provided looks resonable. Only a few $ more than what I've been paying.

I'll probably wait until the "free warrenty replacements" get denied before I get a Stancor. My last one was free. I replaced it a few weeks ago. When I was tealking to the gguy at the counter he said that they might eventually deny the warrenty if they go out repeatedly over a short amount of time. He said they just did that to someone who was going thru 1 or 2 in 3-4 months. They finally told him "no more".

Hey C-man. Madagorda Bay huh!?! I've got familly all over the place down there. Palacios, Port Lavaca, El Maton. Matter-of-fact, we're having a familly reunion this summer at teh church in Blessing.

See ya around.
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