Chevy & GMC Vans

When I turn the key in ignition, accessories do not turn on, no lights. Lights will not turn on at all when car off and usually they would. When I crank, nothing. If I connect a jump pack, I can get the van started. Once started the gauge dials, jump a lil, if I turn the headlights on, the whole thing shuts off.
Voltage of battery while running, 13.3v
Disconnected battery while running and van still runs.
Replaced the ignition switch.
Traced as many grounds as I could find, cleaned with contact cleaner and wire brush and replaced.
When cranking with the jump pack connected, drops to 7v then engines starts and it drops to 3v, then back up to 12v a second later.
Charged battery and tried to start, nothing.
Have traced all ground I could find on engine.
No dice.

Any ideas or tests to do or ideas of what could be wrong.
I’m at a loss for what the issue could be or how to go about fixing it.

1995 g2500

This is what happened on my Silverado. And it's the only time I've ever seen this.

Corrosion had hardened on the battery cables, both of them, and effectively cut off the connection between them and the battery. What I did, I took that center screw out of the cable, took off the colored plastic end, and scraped all the corrosion off the ends. Cleaned up the battery post pads and reassembled. Worked like a charm.

With everything together, you couldn't tell the terminals were corroded. Even when I took them apart, they didn't look like the connection would be disrupted. But you could tell something had attached itself to the eyelet and that's what was keeping the flow of electricity from flowing. It would even loosen the cables. I thought the battery post pad was loose. Nope, just corrosion.

Worth a look anyway.

Hey Mike,
Did you Silverado have the side terminals wires for the battery?
The van does and the whole connection is covered in rubber and a bolt goes through them to connect to the battery.
Did you remove that rubber and then redo the battery terminal connections?
I hope I’m explaining myself okay.
Thanks for your help.

Yes, typical General Motors side post battery. The battery cable itself has a big eyelet on the end of it, and the colored plastic cover goes over that and the bolt goes through the middle and screws into the battery. There is a wire coming off the main cable but that is attached to the cable, not the cover.

That center bolt is somehow molded in with the plastic cover, so it takes a bit to get it in and out. But it does it so you just have to work with it a little. Once that bolt is out, the cover slides off. Once I could get a good look at the cable ends, it was easy to see the green corrosion that was on the ends. I didn't have a good tool to get the corrosion off, so I used a screw driver and scraped until it was all off.

I really hope this is your problem, because an hour's work and the problem is solved. If it doesn't help, then we can come up with something else. Also, while you're at it, check the other end of the cables where they go to the starter and ground for corrosion and tightness.

Mike.
You are a legend!!!!
I just went ahead and replaced the main ground wire and the terminal connector to the positive and it worked!!!

You have no idea how great full I have for your help.
I’d spent hours and hours trying to figure out this problem and was on the verge of giving up.
But your idea and help, helped me to solve the issues

Thanks so much Mike.

The internet is an awesome thing.

Wow you're welcome. I'm not always so helpful... It only took you hours and hours? I took me weeks. I'm glad it worked out for you. An awesome feeling when you fix the car yourself!