VW electrical problem

Boonie Buster · May 8, 2011

What gives!

2002 VW GTI 1.8T

So I replaced the battery 3 months ago. Last night went to start it up and nothing, jump started it, ran fine. Went to start it up this morning, agian nothing, jump started, drove it 30 miles no problem. stopped it and tried to restart and nothing. All the dashlights come on strong, but there's not enough juice to start it, its really slow to turn over and just wont fire up. The battery is reading 12.5v while the car is running, Had the alternator tested, it's fine. There is no resistance in the wires from the battery to alternator. Not really sure what's going on or what else could be the problem....?

We checked the cells in the battery, all fine, i even tried another alternator, same thing.

My alternator is reading 7.6v output...:eeek:

HELP!!! :corn:

I'm just not sure what else to check, we check all the fuses we could find, maybe there is a secret one that VW hid somewhere that we didnt check... :eeek:

Thanks in advance.

skinny_pedal · May 8, 2011

Check the fusible links on top of the battery?

Boonie Buster · May 8, 2011

skinny_pedal said:
Check the fusible links on top of the battery?

Ya, my dad checked all those and didn't come across any bad ones. All were good.

skinny_pedal · May 8, 2011

If your getting 12v at the battery and 7v at the alt. Id double check the fusible link.

Boonie Buster · May 8, 2011

ya, we checked that, looks fine, we're testing to see if there is a draw with everything turned off, looks like there might be. the only thing i have installed that is aftermarket is a Zune connection to the back of the radio, which was done per the isntructions. I'm wondering if that's the issue causing this problem... :eeek: It had a proper ground and power setup....

TrikeKid · May 9, 2011

If you only have 12.5v running, you're not charging. Go over all the charging system wiring, I bet you'll find something loose or corroded. Check the voltage drop between the alternator and battery. (meter on volts dc, lead on the charge wire out of the alt and on the positive of the battery)

Boonie Buster · May 9, 2011

We tested the resistance in the large wire from the alt. to battery and it was fine. that wouldn't change while running would it?

A part of me is still suspicious of a bad alternator, just because I've had the napa tester thingy say it was fine and then go to another store and have them tell me it's not, then get a new alternator and it works fine.

But i did have another alternator in it this afternoon and the same results happened, 12.5v while running with the "new" remaned alternator... :eeek:

I'll double check the wires.:awesomework:

Toyotanut · May 9, 2011

Boonie Buster said:
We tested the resistance in the large wire from the alt. to battery and it was fine. that wouldn't change while running would it?

A part of me is still suspicious of a bad alternator, just because I've had the napa tester thingy say it was fine and then go to another store and have them tell me it's not, then get a new alternator and it works fine.

But i did have another alternator in it this afternoon and the same results happened, 12.5v while running with the "new" remaned alternator... :eeek:

I'll double check the wires.:awesomework:

Does the voltage reading change as your rev the motor? When you tested and got 12.5 volts was that at the battery or at the alternator? Perhaps the signal wire to the alternator (allows the alternator to "turn on") isn't sending voltage.

Boonie Buster · May 9, 2011

Toyotanut said:
Does the voltage reading change as your rev the motor? When you tested and got 12.5 volts was that at the battery or at the alternator? Perhaps the signal wire to the alternator (allows the alternator to "turn on") isn't sending voltage.

We only tested at idle, compared it to my dad's lexus which was showing 14.5v at the battery while idling. mine at idle was 12.5v at the battery. That was with the original alt. and the "new" alt.

That's what my dad was wondering, if the "exciter" wires weren't sending a signal. :eeek:

Boonie Buster · May 9, 2011

Could it maybe be a loose ground wire causing this issue? A guy at work said they chased a similar problem and it was a loose ground wire. They replaced the starter/alternator/battery and nothing solved it but a loose ground wire. :eeek:

skinny_pedal · May 9, 2011

Boonie Buster said:
Could it maybe be a loose ground wire causing this issue? A guy at work said they chased a similar problem and it was a loose ground wire. They replaced the starter/alternator/battery and nothing solved it but a loose ground wire. :eeek:

Did you do an ohm check to see if your ground is any good?

Boonie Buster · May 9, 2011

skinny_pedal said:
Did you do an ohm check to see if your ground is any good?

I think so... I'm far from an electrical expert, my dad was the one doing the testing, he did confirm there were no drains on the battery. I think he checked the grounds this morning. Not sure if he tested the ohms.

How would one do that? he's not here to help, but i'm here and can test it. :corn:

TrikeKid · May 10, 2011

Boonie Buster said:
I think so... I'm far from an electrical expert, my dad was the one doing the testing, he did confirm there were no drains on the battery. I think he checked the grounds this morning. Not sure if he tested the ohms.

How would one do that? he's not here to help, but i'm here and can test it. :corn:

Testing ohms on the wire is really only going to tell you if it's got a connection to the other end or not, you can cut a battery cable down to one strand and it'll show the correct ohm reading without being able to carry **** for current.

Put your multi-meter on the negative of the battery and on the engine somewhere, set to volts dc and see what the reading is, if it's more than a couple tenths of a volt you have a ground problem.

The "exciter" wire your dad is talking about very well may be the cause, is your battery light on on the dash? Because it should be if you're only at 12.5 volts.

Boonie Buster · May 10, 2011

Well, i think the exciter wire was the issue or i guess the alternator needing a slightly better ground. I put a 16ga (or so...) wire from the alternator to the negative battery post and then started it up, with the battery fully charged overnight, checked the volts and it was reading 14.10v. So we will see in the morning if it fires up or has any issues. :awesomework:

zukkev · May 10, 2011

If you're gonna run a redundant ground (wire from alt case to ground at battery)...which isn't a bad idea on these---Use at least 12 ga wire, if not 10...
I see all kinds of rigs today with the alternator not charging, and no 'Charge' idiot light on...Dubs are one of the worst...

Boonie Buster · May 10, 2011

zukkev said:
If you're gonna run a redundant ground (wire from alt case to ground at battery)...which isn't a bad idea on these---Use at least 12 ga wire, if not 10...
I see all kinds of rigs today with the alternator not charging, and no 'Charge' idiot light on...Dubs are one of the worst...

I was planning on putting something a little more permanent in, it's just zip-tied along the original route right now. I think i put a 14ga wire in, if i remember what hole in the cutters i trimmed the edges with. :redneck: It started up and drove this morning. It still has a stumble, like a vaccuum leak of sorts, it sounded like there might be something loose, but wasnt positive.:eeek: Dang VW!:haha: