Glow plug relay keeps going bad
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From: Good old Oswego.
Glow plug relay keeps going bad
Hey guys, I recently replaced my GP's to Beru's on my '84 6.9L. I also replaced my GP relay on the inner fender. I have a switch installed for the GP's because the controller in the back of the engine is junk. After replacing the relay, it worked one time and wouldn't work again so i got a new one and same thing. Anyone have any idea why the relay keeps s*#ting the bed? Is it ok to get rid of the relay and hook the GP's directly to the switch? 
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
You need a switch and wiring that could handle 200 amps.
So eliminating the relay is not really an option.
Follow the orange/white wires from the realy toward the engine.
Right before it gets to the engine, there is a connector with about 6 wires in it.
One end has both the orange/white wires in it.
Look at the connector for signs of overheating or distortion.
If yours is as bad as mine was, it will be melted together bad enough you can't get it apart.
Clip all four orange/white wires as close to the connector as you can, then use solder or another heavy duty connection method to splice all of them back together.
I used a copper split bolt and then taped it up good so it did not short out.
The orange/white wires carry the current to the glow plugs, if the connector is bad, no electricity makes it to the glow plugs even though the relay is working.
So eliminating the relay is not really an option.
Follow the orange/white wires from the realy toward the engine.
Right before it gets to the engine, there is a connector with about 6 wires in it.
One end has both the orange/white wires in it.
Look at the connector for signs of overheating or distortion.
If yours is as bad as mine was, it will be melted together bad enough you can't get it apart.
Clip all four orange/white wires as close to the connector as you can, then use solder or another heavy duty connection method to splice all of them back together.
I used a copper split bolt and then taped it up good so it did not short out.
The orange/white wires carry the current to the glow plugs, if the connector is bad, no electricity makes it to the glow plugs even though the relay is working.
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From: Good old Oswego.
Thanks for all of your replys, I may need to go a little further into this problem. Ok, when I installed a new relay, I tested for voltage to and from it with a multimeter. When I flip the switch I get a little over 12 volts going to it and 12 volts leaving it going to the GP's which means everything is working properly. I will start the truck using the GP's just one time. After that, if I try to turn on the GP's using the switch, I get a reading of 12 volts to the one side and nothing on the other side? Is faulty wiring going to cause this to happen? Another question....what size wiring sould be used from the battery to the switch and from the switch to the relay? Thanks for your help.
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Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
The two small terminals are what activates the relay.
The bottom one has to have a good ground to it. Usually in stock wiring the wire attached runs over to the fender.
The top purple wire is from the stock controller and is where you should be running the wire from your momentary switch. You need to supply power to that terminal to close the relay. Wire size can be small, the amount of power needed to close the relay is very small.
You never said if you are getting power there after the first start.
The right hand big terminal in the picture is the power from the battery, that wire is AWG 8 to the positive battery terminal from the relay and should always have power.
The left big terminal goes to the glow plug harness.
My wiring there is not stock, that blue fusible link is tied into both 10 AWG orange/white harness wires.
Last edited by Dave Sponaugle; Nov 23, 2007 at 11:39 AM.
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Thread Starter
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Joined: Oct 2007
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From: Good old Oswego.
hey dave, I think you just solved my problem. I think i have a few things messed up on that relay. 1- I dont have a larger wire going from the battery to the relay. 2-I have the ground and wire from the switch backwards. Well hopefully tomorrow I can get some 8 guage wire anf fix the damn thing. Thanks for the help!!!!!!
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Which terminal the ground and switch are on makes no difference.
The coil that activates the relay terminates in the small terminals.
Just so one is attached to a good ground and the other gets power from the momentary switch.
The coil that activates the relay terminates in the small terminals.
Just so one is attached to a good ground and the other gets power from the momentary switch.
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