Low Voltage Problems?

[howslowcanyougo]

98 TSi, AWD, A/T.

Last week noticed when I put my brakes on that my radio would shut off, let go of the brakes and it would come back in?

Then getting on the freeway the car started sputtering, and the Battery. a/t temp and oil pressure "triad" of idiot lights started filckering on and off?

Talked to one of my buddys, he said 90% chance of a bad altenator.

Order a rebuilt at Checkers for $170.00 <90 AMP> with lifetime warranty, and installed it. <What a pain, take the damm wheel off to take the splash gaurd off to pull the last bolt out, drill>.

Got in the car, and got the SAME 3 lights, and the brakes STILL brought the radio down?

Read through some more DSM boards and then installed a NEW 750 CCA battery and NEW terminals, cause the old battery was weak, and the terminals were crappy.

I also pulled out the 100 AMP Alt fuse and it tested as good?

Start it up again and STILL get the same 3 idiot lights?

If I give it some gas they turn off after about 10 seconds?

Checked the voltage with a meter, with the car running I get about 13.1, with it off I get about 12.9?

I hate to go through it all over again, but I'm now leaning twords the rebulit Alt I just installed as being a bad rebuild?

Or could the belt be slipping? Just how tight is the alt belt suppose to be anyway? <I've got it pretty damm tight now!>

Else something in the wiring system, God help me there?

Cause the battery, fuse and termials are all AOK?

Any ideas?


:headache: :headache: :headache:

TIA.......


Howie

[blown_turbo_tsi]

i am not a mechanic but i think that you should get someone to push the brake while you are measuring the voltage at the battery and at the alternator and just keep measuring the lines until you find a short somewhere.... it's tedious but it will help you know your car a little better

[Goat Blower]

Sounds like you've got a bad alternator, not a surprise from Checker. You should be getting ~14V at idle and ~14.4V at any higher rpm. Bring it in and have them check it under load on their tester. I've gotten to the point where I have them check before I even leave the store.

[Goat Blower]

And your belt deflection should be 1/2 inch or so at the widest point between two pulleys. It doesn't need to be real tight, you can ruin the bearings in your alternator that way.

[howslowcanyougo]

Thanks for the verification SteveO...

Damm, guess I gotta swap this damm thing out AGAIN already???CRAP! :headache: Guess it's better than having a "mystery" wiring problem plauge! Those kind of woes can be worse than a case of Cancer! I know what I'll be doing again tonight, taking off the damm tire to get to the splash shield to get to the damm last Alt bolt, again.

I'm having Checkers do the SAME thing too, have them test the new, new exchanged one, BEFORE I spend another night putting in a NEW BAD ONE!

BTW:Thanks for the belt deflection spec, thisnk I'm pretty close, but check it out on this next install.

Many Thanks.......

[john]

If I remember correctly, they can check your alternator on the car. Try calling around (checker, bumper-bumper, etc). I don't think it is the belt because it would slip even more at high rpm then. Check it anyways though.

[Kracka]

Checker can check the alt. while still on your car.

[howslowcanyougo]

Yep just drove it into Checker, and had it tested. It's Bad, so they ordered me another and said they'd bench test it BEFORE I install it this time. Live and learn I guess. Thanks for the tip!

[JustROLLIN]

There is one thing that still puzzles me about this mess. If the ALT was bad, then how would the batt. still be reading 12.9v with the car off. If the ALT was bad, the batt would never be recharged and would begin to drop down. Unless, the ALT was charging just enough to maintain 12.8v.

It wouldn't suprise me if the problem persists after you change that ALT out. But, hopefully not.

If it does, go with the voltmeter and test all the way along the brake wiring as already said.

[Alpine TSi]

A perfect battery at its full capacity charge will read 12.6. 6 independent cells at 2.1 volts wired in parallel to bring it it to 12.6. If he has a 750 CCA battery I am assuming he got a deep cycle such as a Optima red or yellow top. Those things can run forever as a starting battery even without the alternator. But yes the alternator was probably just good enough to bring the charge up a little.