glow plug relay ? how to check , - Diesel Bombers

Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

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Old 01-17-2018, 07:13 AM
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Join Date: Jan 2018
Posts: 2
Default glow plug relay ? how to check ,

I put in all new glow plugs and straps, When I turn the key WITHOUT glow plug wire connected I get +12 vdc at glow plug terminal. When I connect glow plug feed wire to terminal and turn key I get 0 vdc. I checked the 175 amp fuse, good. At this point after hours of work Im confused, what is wrong. I have the schematics. What can I check next, sway air intake relay with glow plug relay ??
I have a 2004 2500HD 6.6 Vin1 deisel. any help greatly appreciated, is there a How to check glow plug relay step by step, I took mine out, tested on bench and got voltage to both air intake and glow plug terminals on controller.
thanks all
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Old 01-21-2018, 08:45 PM
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Join Date: Mar 2017
Posts: 130

Probably relay contacts burnt or burnt connection somewhere between fuse,relay or glow plugs. If you can access the relay easily, with glow plugs connected, take a voltmeter and put one lead at the line side of the relay, the other lead at the load side of the relay. With the glowplugs activated, you should get 0 volts, if you get 12 volts, then most likely the relay contact is burnt. If you get 0 volts, take one lead from the load side of the relay, the other lead to the glow plugs, if you get 12 volts, then you have a bad connection between the relay and the glow plugs.
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