stock7

When I pulled up to the light the other night, my car (89 gtu)was acting like the battery was going dead, the tach dropped to 0 and the interior lights starting cutting in and out.. and then it died. I pushed it off to the side of the road, and tried starting it again.. no go, I could hear it turning over, so I kept trying to get it to start, it backfired twice really loud, and then finally started. once it started it ran really rough,and the lights where cutting in and out again, anytime, I would turn on an interior lights, touch the sun roof power switch, turn on the headlights, change gears, release the clutch... it would die. I had it towed to Les Scwabb, and they have no clue what is wrong with it, it isn't the alternator, or the battery. I think it may be a voltage regulator? but other than that I have no clue.. the car is sitting over there, I had to walk over there yesterday, to have them take a look at it...
Anyways if you can think of anything please suggest it.. I am at my wits end with this car.
Matt.
P.S It has a new engine(less than 2 months old) new tranny(3 days old) new exhaust( less than 6 months old)...the battery is les than a year old as well.

Icemark

What was the voltage when it is having problems? (you have a voltmeter right on the dash in the GTU).

Sounds like a bad alt to me from your description.

BTW: the voltage regulator is built into the alt.

stock7

Well, I hooked it straight up to a battery charger, and it still did the same thing. even on starting power... this is what lead me to believe that it isn't the battery or alternator.

Icemark

I also would check the fuse box terminals under the hood (sometimes the 80 amp fuse unbolts), but if the head lights worked, then it points more towards a dead battery and failing alt.

stock7

yeah, the fuse box is in place, thanks though. maybe someone else will be able to help...

cymfc3s

you need to do a thorough check of all the wiring to and from the alternator, battery and the master fuse. Im guessing its wiring. Youd be surprized, ive seen cars have weird problems like this and it turns out, i found rats had chewed through some of the wiring to the alternator. Good luck.

stock7

the strange thing is, It was running absolutley fine. It just dided. Nice car.. I love the Fc2000 front end

RotaryForce13B

I would have to say bad alt.! My 90 GXL did the same thing and it turned out to be the alt. If you can get it running check the voltage with a voltage meter at the alt.

SureShot

So far every one has covered the + side.

Now check the grounds.
With the engine running & the headlights on- voltage drop from the alternator frame to battery neg should be near zero.

stock7

well, the reason I ruled out the alternator, is because I set the charger to starting power, and tried starting the car, basically off of wall power.

Mr. Gadget

Well, if your battery is dead, you have done nothing to start the car. Frst, charge the battery completly.



With all due respect, Icemark has some 9000 posts. I am sure I have read half and don't remember him ever giving bad advise. What he is telling you is sound advise. And also keep in mind that your trying to diagnose a car off the internet, not the simpelest of things to do.

Icemark

That just makes no sense. You can't rule out the alt because you have a battery charger hooked up. What is the max amp out on the battery charger??? 50 amps in crank mode at the most?? (That is the most common).

Barely enough to even crank the car over, well alone start it.

And if you have a completely dead battery (or a battery with bad cells), a charger is not going to put out enough to start it at all.

Maybe if you charged the battery overnight, and then hooked up the battery charger to crank mode and tried to start the car...

Icemark

Thanks for the kind words, but remember on the internet, a high post count does not always mean that the answer is right (even though yes this case the answer is probably right).

stock7

The battery was fully charged, when I tried starting it.. and it had the same results..

SureShot

As I keep saying: "Grounds get no respect."

stock7

Will an FD Alternator mount on the 89 gtu block? and would there be any advantage with going with one?

SevenGirl

Yes and maybe but help others help you by providing direct answers to voltage questions that may lend a solid and quicker diagnosis. See "Silverrotor" for FD alternators.

Icemark

What was the voltage of the battery when "fully charged"???

Templeswain

The alt is one of the easiest things to take off.

Take it off and take it to napa and have them test it for you.

This way you'll know its not the Alt.

And I second icemarks motion.

Your problem sounds like an alternator just decided to die out. But whatever. Could be your ground slipped off the firewall slip connector. Could be the chupracbra.

Good luck.

stock7

Will do, thanks guys

stock7

Ok Guys. It has been 2 months and I am still stuck.. Please Please Help. I replaced the alternator..Didn't help (Excellent support from Silverator Btw.) I also replaced the Leading and Trailing coils..Still no go. I Replaced the Mass Air Flow Sensor.. So I had it towed to a shop. They tested the ECu, and told me it was bad. I ordered a New(Used) one that came out of a runnig 7... The car ran for 5 mins and then died.. The issue was with spark, the old Ecu was not sparking, and the new one did.. but now isn't. I did a continuity test from the ECu to the coils, and they passed. What Now?? Would putting the N351 Ecu, in place of ther N350 ECu cause this? I am at my whits end.. I seriously need help guys.
Thanks,
Matt.

ROTILLA

As I keep saying: "Grounds get no respect."


I agree, sound like a ground to me. Check the grounds from the motor to the body, that is where the computer is grounded to(the body). You can run a temporary ground to the body yourself and see if that fixes the problem. If it does, then you can find tha actual one that has worked loos, or decayed to uselesness.

Leslie

Dltreezan

iTrader: (3)

come on guys lets help him out its been months plus the kit you guys want me to build anytime soon depends on his car running. Lets get this s5 back on the road!!

stock7

When I checked, the voltage at the Coils, I am getting a reading of 7 Volts. From everything that I have read, it should read 12V. if this helps at all. I am also Checking out the grounds.. Thanks.

HAILERS

stock7.....do you have a digital meter and more or less know how to use it? No sense in asking you to check anything if you don't have a meter. I'm not into the parts changing business when it comes to cars.

About grounds: The ECU is grounded on the top of the rear rotor housuing. The housing is a part of the engine. The engine has this hugemongous cable that runs from it to the negative terminal of the battery. That should be good enough, especially since that same cable is attached to the chassis just under the left strut tower. It ain't a ground problem unless the ground terminals on top of the rear rotor are not connected.