Strange wiring issue..

[Driftwood]

Trying to figure out what is going on with the wiring in my truck (SD22). I'm not very knowledgeable testing electrical systems and for a novice it can be hard to know where to begin.

When I have the ignition set to "ON" position it warms the glow plugs. The light will stay on indefinitely and there is no audible click from the glow plug timer leading me to believe that the timer is faulty. "ON" position drains the battery. For some reason the alternator doesn't appear to charge the battery. I can only use the directionals in the "ON" position.

When in "Accessory" position all the electrical (wipers, headlights, heater, etc.) work but the glow plug light turns off. In "ACC" mode the alternator charges the battery. This is the mode I usually drive in and switch over to "ON" position when I need to use my signals. Kind of strange but I've gotten used to driving it like this. I then switch it back to "ACC" so not to burn out the glow plugs.

It has been suggested to me to just replace the whole wiring harness all together. I can't help but think it may be a simple fix, I'm just overlooking something. Could it be a faulty relay? Has anyone had this problem or have any suggestions? Ideas where to look first?

Thanks,

O.D.

[waynosworld]

Do you have all the diesel electrical accessories, DPC module, glow plug timer, and the injection pump controller, and do they all work properly, meaning when you turn the key off, does the engine shut down, or do you have a choke cable to shut the engine down?
Have you tried another glow plug timer?

[asavage]

When in "Accessory" position . . . This is the mode I usually drive in and switch over to "ON" position when I need to use my signals.

The truck should not run in ACC position. As it does, there's something amiss. Whether it's a faulty Ign. switch or not I can't say. Has the wiring been modified? If not, I'd be looking hard at that Ign. switch.