Gentlemen,
Just changed out my 8 year old set of batteries from my 86 GMC 6.2 Diesel. Problem is I waited several days before reinstalling them due to heavy snow pack and there is one wire I can't remember where it goes. Looks like a 14 to 16 gauge black wire coming off of the alternator. Can't remember if it goes to ground or to the plus side of the battery. Reason I decided to change out the batteries couldn't get any glow plug action. Thought it might be because the batteries were weak. Not sure if this one wire is the magic key to initiate the glow plugs or what. Purchased a Hayes book from Advance auto and their diagram was no help what so ever. I know this wire goes somewhere either plus or negative, but want to make sure we don't blow up a good alternator or batteries in the process of connecting it.

Any knowledgeable help will be greatly appreciated.

Making Tracks

 

i would go get some some wiring schematics. check your local libarary for some old manuals. i know mine has but i live in a pretty big town. go to a shop that you know had alldata or mitchell and ask to look it up on there.

 

Woody35,

I appreciate the tip on the manual searches. I took my Hayes book back to Advance Auto and got creative thought as I pulled into the parking lot. I asked to see a replacement alternator, knowing they have a wiring diagram and sure enough it answered my question as to where the wire went. Though black in color, it did go to the plus side of the battery. Still no glow plug action. With two 926 amp batteries, should be enough juice to turn them on. I looked in the owner's manual to see which fuse in the panel controlled the glow plug module. Naturally, it didn't show Jack as to which fuse does the trick. Guess tomorrow, with trusty volt ohm meter in hand, I will pull each fuse out and check them one by one. Is there any other test that I can do to check this out that you are aware of? I hate to call the mechanic for something that I could have found on my own. Truly need to get this back on the road. Have to put it to work once again. Much to move with it. Thanks again for your help,

Making Tracks

 

did you check your glowplug relay? common problem on these trucks.