1999 GMC C6500 Topkick No Power

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Oldgator73

Oldgator73

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Joined
Dec 28, 2017
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Location
Dover, DE & Mouth of Wilson, VA
My son has a 1999 GMC C6500 with the 454 gas engine. He drove it to our house yesterday and when he started to leave it wouldn?t start. Everything dead. No lights, no nothing. He purchased a new battery and installed it. Still nothing. He jumped it from my truck and still nothing. Thinking it could be the master fuse or a relay. Any ideas. Before anybody asks we have not found a master fuse and what my son and I know about auto mechanics will not even fill a paragraph.
 
If everything's dead, I would start at the battery with a test meter and start working my way to the first connections. I would start with the ground cable to make sure you have a good ground Connection(s). Then start following the positive cable until you hit a fuse or fuse block.
 
Gizmo100 said:
If everything's dead, I would start at the battery with a test meter and start working my way to the first connections. I would start with the ground cable to make sure you have a good ground Connection(s). Then start following the positive cable until you hit a fuse or fuse block.
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It could be a fused link, a fuse that does not look like a normal fuse. It often looks like an ordinary wire but may have a tab on it. They are usually located in the wiring near the alternator.
 
My son ordered a tester. Should be here tomorrow. We will go over the entire electrical. I have a vested interest in this since I have 26? former Uhaul van parked in front of my house.
 
Oldgator73 said:
Everything dead. No lights, no nothing.
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That sounds like a complete wire failure.  Probably the main wire from one of the battery terminals.  I would first check ground, like negative from battery to engine block.  Etc.  You can take the jumper cables and put one on negative, one to block, and see if you get lights.  If you test on the positive side, make sure jumper cable does not touch the car / (anything ground), but again, you can check for complete cable failure with jumper cables.  If the lights come on when you bypass a wire, that would be a point of interest.
 
SpencerPJ said:
That sounds like a complete wire failure.  Probably the main wire from one of the battery terminals.  I would first check ground, like negative from battery to engine block.  Etc.  You can take the jumper cables and put one on negative, one to block, and see if you get lights.  If you test on the positive side, make sure jumper cable does not touch the car / (anything ground), but again, you can check for complete cable failure with jumper cables.  If the lights come on when you bypass a wire, that would be a point of interest.
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Thanks. When he gets here today we?ll try that.
 
I have a 1997 pick up with the 454.  If just did just did something similar. I ran it for about 20 mintutes as I was planning to move it the next day to storage. The next morning there was no electrical. This had never happened before. Battery is 2 yrs old. I wiggled the battery terminals a little and tightened then slightly and it fired up. I hope yours is this simple. I do not like the side post system. On mind there are two that overlap each other on the positive side. One theory is if they are mounted so the weight of the cable is coming off to the side instead of straight down, gravity, bumps, vibration can work against this and loosen the connection over time-this seems possible if this overall action moves CCW to loosen the bolt.  My son has had this happen a couple times on his 1998 pick up that had partially stripped threads on the battery.
 
My son purchased a new battery with the terminals on the top. But he still has no electrical. We did as SpencerPJ suggested and jumped the ground but still nothing. Now the task starts of tracing from the battery to the fuses.
 
Good luck, I hate electrical troubleshooting.  :-[
With such a complete failure, check main lines first.  It's not going to me some little 15amp fuse. I've never known of a 'main' fuse that cause complete lights failure.
 
Found the problem. It was a low voltage switch. We had power going in but none coming out. The switch is inline from the battery to the fuse box. My son bypassed the switch by putting both wires on one terminal. He brought the switch in and it smelled burned. We took it apart but couldn?t see anything. There was a phone number on the case so he called it and left a message. They called him back today and said it was a low voltage switch installed on all Uhaul trucks for one year. He said it wasn?t need and told my son to just bypass it, which he had already done. Problem solved. Thanks for all your input.
 
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