Greetings MYF,
A saying that I happen to agree with is that you don't fail until you quit. I know what it's like to have a
project get bad stuck, and you start to get the feeling that this is going to become a failure that will color
how you feel about your ability to keep something rolling down the road. :-(
But then I'd finally decide to reach out to a a mentor and ask for help, and to my surprise they would coach
me on the repair until the yard art was transformed back into solid transportation. They would use the broken
machine as a real world training exercise. And when I asked them why they were willing to help me, they
would simply reply that they remembered what it was like to be stuck, and have an elder help
them.
So we're here to help. And it's possible to pull this off -- awhile back some guy had been given a GMT400
for free because it had bad electrical problems, but over time we worked through the issues methodically,
and the last we heard from him he was pretty happy with how it turned out...even at night. :0)
****
Enough setting of the dinner table. As long as your truck is wounded but stock, then with the Factory Service Manuals
we *can* get this sorted out. First things first. When you have electrical failures that make sense but can't be fixed by
swapping parts, then it's usually a power problem. But when you have illogical (ie: functionally unrelated) electrical problems,
it is usually traced back to a
shared ground. And these can test the patience of even the most seasoned troubleshooter.
So I propose to give you a quick tutorial on how to take weird failure symptoms and locate a shared electrical connection between them.
OK. You have a '97, but I've discovered that the '99 FSM (Vol 4, Electrical Wiring section) is pretty much identical,
so I opened up the copy on my laptop and started scanning the ground distribution diagrams looking for anything
shared by the headlight & windshield
washer wiper circuit. Check this out:
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Of course, with nothing more than the symptoms you shared this isn't incontrovertible proof that G200 must be a marginal ground
and is the root cause, but by the same token the headlights and windshield wipers are on separate power fuses and are otherwise functionally
independent. But the control modules for these 2 systems
do share the same ground. And when electrical circuits backfeed
through other circuits due to a shared marginal ground you can experience some pretty weird symptoms. As a matter of fact there's
plenty of real world examples illustrating this sprinkled throughout the forum.
Since we now have a troubleshooting interest in
G200, is the location of G200 documented in the '99 C/K Electrical Service Manual?
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In the general area under the steering wheel on the inside of the dash is the physical location of G200.
WITH THE BATTERY DISCONNECTED, remove G200, clean every surface back to shiny metal, and reassemble/secure
this ground. If this solves the interaction issue, great! If not, your time was not wasted, for grounds in new
condition just make all subsequent electrical troubleshooting in the area that much more clear & unambiguous.
Speaking of which, on a truck this old it would well worth inspecting/renewing every ground on the truck. Fortunately,
the General has a short list of every single ground in the wiring harness. (See 1st attachment for the list.)
****
To test the bulb, did you just apply +12V and used the existing ground? Or did you use 2 wires (+12v & ground) in order to test the bulb?
I'm trying to figure out if G113 is a suspect ground or not:
You must be registered for see images attach
By the way, if you would like a brief tour of how the electrical wiring system is laid out in the General's
Factory Service Manuals, then head over hear and give this a read. (
Wiring diagram info in the FSM)
Since you haven't been all that active in this forum, I'm going to assume that you are not aware
that thanks to the efforts of others there are the factory service manuals for your vehicle available
for free download over
here. If you haven't already done so, give yourself the gift of the best
documentation available to use when troubleshooting/fixing your GMT400.
****
I was going to start in on the spark/no start after issue, but this is already longer than it should be.
If nothing else, from this point forward whenever you are getting ready to move any part of the wiring
harness around (either to Facilitate Other Maintenance or post repair reinstallation) ...
never do this with
the battery connected. It's just too easy to have a momentary slip, arc is generated, and suddenly
POOF $$$ go up in smoke. Myself, I learned this the hard way, and in 20/20 hindsight what happened
to me was all too predictable. But at the same time I appreciate your honesty, and between our 2 stories
hopefully others reading this thread while researching similar issues will be able to learn from our
misadventures and avoid doing this to themselves.
We covered a lot of ground, but again as long as you can get the wiring on your truck back to stock
(if any mods have been made) ...then between the all of us we should be able to get your truck
back on the road and once again earning it's keep.
Hope this helps. Best of luck. And let us know what you discover.
Cheers --