QuestionThis one's a real mellon-scratchy... Sorry for the length, but its worth it...
I have a 1989 GMC Vandura G3500 6.2 L diesel on a short bus frame. I know your not a diesel expert, but the problem is more electrical than glow plug related... So recently I was driving, 4 hours into a 20 hour trip. I'm not sure exactly when, but my glow-plug indicator lamp became dimly lit, and the voltage meter on the dash took a big dive, and so it seemed there was lots of power getting sucked to the Glow Plugs.
I thought it was something faulty with the Glow Plug temp sensor, but I'm pretty sure I have ruled that out... I disconnected all of the wires on my Glow Plug controller (a 4 wire harness + 2 larger power wires). The GP indicator lamp still dimly lit, despite power being cut to the individual GPs. Also, the Voltage between ground and each individual GP was only 0.02 V when the GP indicator light was on, and I don't think each GP runs off of 0.02V. This brings me to my first question- have I ruled out the Glow Plug system as the problem?
Asuming that I have, i ran a ton of tests, and to keep a long story short I've found this: When my lights are on - and this includes headlights, brights, turn, brake, CLPs (the running lights on top), dome lights, and dash lights- I see that the GlowPlug indicator light is lit. It becomes brighter as more and more lights start coming on.
I can stuff a ground wire (going directly to ground) on to the black wire terminal coming from the GP indicator light, and the light will shut off. I can hook an ammeter up to that ground wire, and as I turn lights on one-by-one, I see a current flow going from 0 amps all the way over to 12 Amps!
I've checked for grounding wires being loose or disconnected, and I can't find any. I've looked for melted wires, cut wires, and any other mess i could find... NONE.
Do you have any idea whats causing this short?
Would it be a bad idea to just quick fix-it, and run a more-permanant wire from the neg side of the GP light directly to ground?
HELP & THANKS!
AnswerWow. You have a pretty stange case I must say. There is no single answer for that, the only thing I can do is offer you some advice. From what you are describing, something is backfeeding through your GP light circuit. I suspect it is one of your lighting circuits. What you can try to do is start to unplug all your lighting circuits one by one, checking your GP light after each one. Hopefully you can find one that makes the light go out. That won't solve your problem, but atleast help to isolate the circuit with the problem. That is the key, to isolate the circuit with the problem, likely a ground problem. Double check your engine ground/battery ground and any other grounds you have, if you have trailer wiring triple check that, they are a hotspot for corrosion and wiring issues.
Hope this helps.
