Wiring issues

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Caman96

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Regarding battery disconnects, I really don't like the exposed blade switches, even if you're putting them on the ground side.

3x the price, but far safer and less prone to corrosion. This one's also rated to carry starting current.

If you're expecting to shut off power while the engine's running (emergency shutoff), you'll want a four pole switch so you don't spike the alternator.
Yeah, that looks really dangerous. An “exposed” negative terminal. What battery terminal “isn’t” exposed?
Picture was taken yesterday, 2 years like that…zero corrosion. I maintain my stuff.
You must be registered for see images attach

…and always install on the negative side!
 

Road Trip

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I did the trick with the test light where you bridge the neg cable & the neg post on the battery to see if you got a short & it lit up. Then I went to the fuse box & started pulling fuses one by one & when I remove the BAT fuse, light goes out.

Hello again MYF,

We have yet to touch on this, but I decided to take quick look and see if we couldn't use your test
results to help illustrate how to troubleshoot an issue like this using the wiring diagrams in the FSM.

****

First of all, I decided that with my luck using a '99 manual to assist with your '97 vehicle just sets
us up to trip over any differences between the models. And navigating through electrical wiring
diagrams is already tough enough without further clouding the issue. So I've switched to using
the '97 FSMs, and I recommend that we standardize on them for this repair effort.

So the first thing I wanted to find out was more about the BAT fuse. From previous experience I
know that on the '96+ models the Battery is first connected to the Underhood Fuse & Relay block
prior to being fed to the IP fuse block & elsewhere.

So I needed to know which fuse in the Underhood Fuse Panel is the 'BAT'?

You must be registered for see images attach


So the Battery Fuse looks to be in position #7. (Keep this in the back of your mind for the next diagram.)


So when I'm working an electrical issue, I always like to start at the page where the battery is drawn,
and trace the circuit all the way from there. So here's the first page where I found both the 12v
battery as well as the BATTERY fuse:

You must be registered for see images attach



Putting these 2 diagrams together, now when you unplug/plug the BATTERY fuse in the Underhood
Fuse Block now you can see which fuses downstream in the (in cab) I/P fuse panel are involved in the
parasitic drain you discovered.

Don't know as of yet whether the draw is a feature or a fault. Once you track the current draw down to a
specific I/P fuse or specific electrical load we'll have a better idea. Possibly at some point down the road
we will decide to switch from a test light to quantifying the size of the current drain with a multimeter.

But the point is, if we treat the wiring diagrams like a road map, then since we're primarily dealing with
straightforward +12v DC we should be able to get this figured out.

By the way, while we are here I'd like to take a little mystery away from the way these wiring diagrams
are marked up. For example, the wire coming from Battery Fuse #7 has "5 Red 142" written next to it.

The '5' is the size of the wire in metric-speak, the Red is the color to look for, and 142 stands for unique
electrical circuit #142. Having spent a lifetime working with classic wire gauge numbering, if you tell me
to look for a 16 gauge wire vs a 4 gauge wire, I can easily visualize one is a lot larger than the other.

By the same token, I still have difficulty with taking a metric size & being able to visualize it. For me,
the attached translation table is a huge help when I'm reading the wiring diagram and trying to find
the matching physical wire in the vehicle.

****

No doubt at the outset that all this looks to be a huge grind, but once you fix a couple of electrical
issues and start to get the hang of navigating through the diagrams it's not nearly as bad as it
initially seemed.

One last thing. No worries about how you tested the headlight bulb. It just means that all we
need to do is verify that +12v is being sent to the bulb connector, and also verify a near-zero
resistance between the ground pin on the bulb connector and G113.

Best of luck with your hunt.
 

Attachments

  • wire size table - metric vs gauge - 99 Chevrolet & GMC CK Truck SM - Vol. 3 & 4.jpg
    wire size table - metric vs gauge - 99 Chevrolet & GMC CK Truck SM - Vol. 3 & 4.jpg
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Last edited:

MurderYurFace

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Hello again MYF,

We have yet to touch on this, but I decided to take quick look and see if we couldn't use your test
results to help illustrate how to troubleshoot an issue like this using the wiring diagrams in the FSM.

****

First of all, I decided that with my luck using a '99 manual to assist with your '97 vehicle just sets
us up to trip over any differences between the models. And navigating through electrical wiring
diagrams is already tough enough without further clouding the issue. So I've switched to using
the '97 FSMs, and I recommend that we standardize on them for this repair effort.

So the first thing I wanted to find out was more about the BAT fuse. From previous experience I
know that on the '96+ models the Battery is first connected to the Underhood Fuse & Relay block
prior to being fed to the IP fuse block & elsewhere.

So I needed to know which fuse in the Underhood Fuse Panel is the 'BAT'?

You must be registered for see images attach


So the Battery Fuse looks to be in position #7. (Keep this in the back of your mind for later.)


So when I'm working an electrical issue, I always like to start at the page where the battery is drawn,
and trace the circuit all the way from there. So here's the first page where I found both the 12v
battery as well as the BATTERY fuse:

You must be registered for see images attach



Putting these 2 diagrams together, now when you unplug/plug the BATTERY fuse in the Underhood
Fuse Block now you can see which fuses in the fuse panel are involved in the parasitic drain you
discovered. Don't know as of yet whether the draw is a feature or a fault. Once you track the current
draw down to a specific I/P fuse or load we'll have a better idea. Possibly we will decide to switch from
a test light to quantifying the size of the current drain with a multimeter.

But the point is, if we treat the wiring diagrams like a road map, then since we're primarily dealing with
straightforward +12v DC we should be able to get this figured out.

By the way, while we are here I'd like to take a little mystery away from the way these wiring diagrams
are marked up. For example, the wire coming from Battery Fuse #7 has "5 Red 142" written next to it.

The '5' is the size of the wire in metric-speak, the Red is the color to look for, and 142 stands for unique
electrical circuit #142. Having spent a lifetime working with classic wire gauge numbering, if you tell me
to look for a 16 gauge wire vs a 4 gauge wire, I can easily visualize one is a lot larger than the other.

By the same token, I still have difficulty with taking a metric size & being able to visualize it. For me,
the attached translation table is a huge help when I'm reading the wiring diagram and trying to find
the matching physical wire in the vehicle.

****

No doubt at the outset that all this looks to be a huge grind, but once you fix a couple of electrical
issues and start to get the hang of navigating through the diagrams it's not nearly as bad as it
initially seemed.

One last thing. No worries about how you tested the headlight bulb. It just means that all we
need to do is verify that +12v is being sent to the bulb connector, and also verify a near-zero
resistance between the bulb and G113.

Best of luck with your hunt.
Thx again man. I hope it doesn’t seem like I’m stalling. It’s just that I’m at work right now and I can’t physically check on anything in my truck at the moment but when I get back home later, that’s the first thing I plan to do.
 

Road Trip

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Thx again man. I hope it doesn’t seem like I’m stalling. It’s just that I’m at work right now and I can’t physically check on anything in my truck at the moment but when I get back home later, that’s the first thing I plan to do.

No worries, no rush. We all realize that life happens and that we're all fitting this in
whenever a free moment allows us to do so. I know I've got deadlines looming
having to do with an upcoming move, so I'm going to be a bit spotty in here myself.

But the good news is that there are others who will be able to step in and keep the repair
project moving forward with you. And the cool thing is that once we're done and
you've documented the fix others can learn from your experience as well.

It's all good.
 

MurderYurFace

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No worries, no rush. We all realize that life happens and that we're all fitting this in
whenever a free moment allows us to do so. I know I've got deadlines looming
having to do with an upcoming move, so I'm going to be a bit spotty in here myself.

But the good news is that there are others who will be able to step in and keep the repair
project moving forward with you. And the cool thing is that once we're done and
you've documented the fix others can learn from your experience as well.

It's all good.
Currently in the process of converting everything back to stock. I’ve had this truck for 7 years & have done a handful of things & now I’m following your advice before continuing. Apparently I spliced in a new headlight switch connector a few years back & while it doesn’t look half bad, it prob is lol
 

MurderYurFace

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No worries, no rush. We all realize that life happens and that we're all fitting this in
whenever a free moment allows us to do so. I know I've got deadlines looming
having to do with an upcoming move, so I'm going to be a bit spotty in here myself.

But the good news is that there are others who will be able to step in and keep the repair
project moving forward with you. And the cool thing is that once we're done and
you've documented the fix others can learn from your experience as well.

It's all good.
Good news! I literally just got my truck to start. I traced the wiring thoughout the entire harness. I pinched a wire when I replaced my transmission & that was the problem. After I did the repair, which actually entailed removing the tranny from the block just enough to get the wire out of there lol, the truck started on the first try. I’m still having that issue with the driver side hibeam & wipers. (When I turn on the hi beams my wipers come on also & driver side hi beam is dead. Bulb is fine.)
 

MurderYurFace

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No worries, no rush. We all realize that life happens and that we're all fitting this in
whenever a free moment allows us to do so. I know I've got deadlines looming
having to do with an upcoming move, so I'm going to be a bit spotty in here myself.

But the good news is that there are others who will be able to step in and keep the repair
project moving forward with you. And the cool thing is that once we're done and
you've documented the fix others can learn from your experience as well.

It's all good.
I also noticed that when I give it some throttle the rpm gauge doesn’t move. That’s not right, is it? Doesn’t the gauge get that reading from the CPS?
My scan tool also cannot connect to the on board diagnostics… that’s a new one. Hmmmm
 

Road Trip

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I pinched a wire when I replaced my transmission & that was the problem. After I did the repair, which actually entailed removing the tranny from the block just enough to get the wire out of there lol, the truck started on the first try.

Glad you were able to get the truck starting once again - progress is being made. Speaking of which,
can you get a clear picture of the wire that had been pinched between the engine & transmission? Or if unable to do that,
what is the color code of the formerly-pinched wire?

This may be an important clue as to which exact circuit was shorted and possibly lead us to the cause of the current
symptoms. One step at a time, and between the all of us we will outlast these electrical issues. (!)
 

MurderYurFace

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Glad you were able to get the truck starting once again - progress is being made. Speaking of which,
can you get a clear picture of the wire that had been pinched between the engine & transmission? Or if unable to do that,
what is the color code of the formerly-pinched wire?

This may be an important clue as to which exact circuit was shorted and possibly lead us to the cause of the current
symptoms. One step at a time, and between the all of us we will outlast these electrical issues. (!)
Can’t remember off the top of my head but when it’s daylight out again I will go under & take a look. Wont be hard to find. Will update you on that soon. Ty again; I just leveled up in my automotive electrical skills bc of y’all!
 
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