I'm new, and I need some help with my 89 7.3 turbo GPC. I'm not getting power from the controller's yellow wire to the glow plugs. I have changed the relay and the controller, but still no voltage with the key on. I have power to the 10 g yellow wires from the harness, as well as voltage to the two smaller terminals. I have tested the ground. It doesn't matter which relay (I have two new ones, and one old one), or which controller I use (I have two used ones and one new one. No power to the yellow wire. I also replaced the glow plugs, and still nothing. I could use some help.

 

check the continuity of the yellow wire, it could be grounding out someplace and need replaced, on mine i just used a horn button and bypassed the controller for the glow plugs, worked great.

 

Thanks, I'll check it today. The more I read on this forum, the more I'm leaning toward the by-pass. I just don't understand why it's the yellow wire on all three of my controllers. I have power to the other 3 terminals, which would not be happening if the controller wasn't grounded. I read somewhere that the two smaller terminals should only have 8 volts with the key on, but these have 11 and 12v's. I don't know if that's an issue or not....

 

I checked the continuity of all the wires on the controller. I bench tested the relay, and it cycles correctly. I get 12v to the constant power supply (double yellow 10g wires from the harness), as well as voltage to the white and red wire terminals (the small terminals) with the key on. I still get no power to the large terminal where the yellow wire form the controller connects to the relay, yet my meter shows 12 v. My test light will not activate on it. It's driving me nuts....I'm going to take your advice, and work around the relay with a switch.

 

They could have given you a bad relay

 

I've exchanged the relay twice, with the same result. I'm still without glow plugs, which isn't an issue right now with the warmer weather. I guess I'm going to have to hire a pro to deal with it. I just ain't smart enough to figure it out.