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2K views 5 replies 3 participants last post by  sunshinecc 
#1 ·
My son returns from Tasmania in a few weeks after being gone for a year. As a treat I thought I'd have the headliner in his 2005 Jetta that's been sitting in our driveway for the duration replaced. I did and it looked great, but the battery was dead when I picked it up. Battery indicator light had flickered on the way to deliver the car, but I thought maybe the battery was low and needed to charge up a bit.

The gentleman who'd done the work had a spare battery we used to jump start the Jetta and it started with no problem. As soon as we disconnected the clamps, however, the car ran for about 30 seconds and died despite the fact I was compressing the accelerator in a lively manner. Now I'm thinking very dead battery in tandem with an alternator that's not charging and causing the electric fuel pump to die. Off to the parts store and back with a new fully charged battery (old one was indeed shot, but was from the factory and nearly 10 years old; full marks on the battery VW).

Here's where it gets wild. Hooked the new battery up and as soon as the connection was made it seemed like everything in the car energized: fans, wipers, headlights, the works. None were switched on, though, and there was NO KEY IN THE IGNITION! Additionally, when the key was inserted it wouldn't turn over.

So, groovy guys and girls, do you think that:

A) East Tennessee rodents have chewed through the wiring harness over the winter in a place I can't see (like behind the dash) leaving me with an electrical short powerful enough to melt that 110 amp fuse on the battery (which it did) and a 25 amp engine control fuse (which it also did).

B) The nice old guy that did a bang up job replacing the headliner accidently mashed some wires together in the process.

C) The alternator is shot, but not before it managed to fry things.

D) None of the above. This is just proof that no good deed goes unpunished.

I've checked for the dreaded coolant migration into the harness wiring and there appears to be none. Ideas?





C)
 
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#2 ·
Having fun yet? No guess not, problems like you have are never fun. I'd say A, B, C, & D are all possible but that won't fix anything. When you say "melt" fuses are they really melting or just blowing? The difference being a dead short will blow a fuse, pop it's done where and overload condition will gradually overheat then melt the fuse.
I worry about your ECU and would disconnect it until you can hookup a battery and not have anything fry. I've seen alternators go bad (on other makes of cars) and literally short to ground so I would disconnect the primary cable from the alternator, big cable, a.k.a. battery cable, biggest cable on back of alternator, then hook up the battery.
When things get really bad I've had to remove every fuse and relay (keeping track of who goes where), hook up power then start plugging things back in until you get trouble. Rodents can absolutely ruin your day and why the Germans use some of the crappiest insulation on their wires is beyond me. Don't be surprised if you find crumbling insulation inside harnesses.
Good luck and I'd like to say have fun but you won't. Post back if you get anywhere.
 
#4 ·
Thanks, guys! Well, I hate to admit publicly that I had the battery posts flipped around, but I will. Wow! I used to farm and had lots of equipment with 12 volt batteries. I NEVER made that mistake. First time for everything, I guess. Boy did I feel stupid.

The blown 110 amp fuse was in the circuit with the alternator and likely saved it. As it turned out the voltage regulator was in the process of dying and was likely responsible for the dead battery. . . that and the fact that the battery was almost 10 years old! We're up and running with no. . . well, almost no warning lights.

Thanks!
 
#5 ·
^^ i've done that before on a vehicle. didn't reach the blowing the fuses stage though. i tried putting the positive battery terminal on the negative side post and the bolt was the wrong size and wouldn't fit; oops.
 
#6 ·
Dude!!!...You are so lucky. Go play the lottery right now and place a bet on the Belmont for this weekend. Thank the Gods of circuit protection and a nice complementary note to the fuse manufacturer would be in order too.
I never get that lucky, it would of been spark and fire and burn to ground for sure. Friend of mine seems to be mildly dyslexic when it comes to polarity and has done it three times, once to a car, then a tractor, just recently a hi-end Zero-Turn mower. The tractor and mower weren't too bad but the wife's BMW was nearly four grand in repairs.
Takes an upright guy to admit this, :clap:to you...Cheers!
 
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