is my alternator shot?

[my95tsi]

Ok here's the scenerio.....While i'm driving my car get 13.6-14 volts no matter what. When i'm stopped with no lights on the car get about 13-13.5 volts. While i'm stopped with the lights on the car gets down to 12.5-12.9 with no brake on, with the brake depressed the voltage drops to 11.2-11.9 depending on how many other things are on. Having the brake depressed kills my voltage. The car never whines or dies. It actually has yet to die. Sometimes the rpms drop by 100 or so but it doesn't hurt anything. The battery is also fine. But from what in know about alternators it should never get below 12volts.

 

[GTM]

Originally posted by my95tsi
Ok here's the scenerio.....While i'm driving my car get 13.6-14 volts no matter what. When i'm stopped with no lights on the car get about 13-13.5 volts. While i'm stopped with the lights on the car gets down to 12.5-12.9 with no brake on, with the brake depressed the voltage drops to 11.2-11.9
...

Normal battery is 13.2, charging v. should be between 14.2-14.6. Do you have 2 wires plus the large B+ wire to the battery?

If 2 wire: with a test light connected to ground confirm power to the large B+ wire, probe 2 wires in the plug with the key on. One wire should be as bright as the B+ the other much dimmer. If not then your brushes/ slip rings, rotor windings are bad. If yes then you may only have 1-2 diodes of 6 that are not burned out. You will need to replace them or the whole Alt.

Cheers,
GTM

 

[Defiant]

And check your belt adjustment.

 

[GTM]

Originally posted by Defiant
And check your belt adjustment.

Yeah, and that too.

Do the '95s have 2 or 3 wire plug? I need a schematic showing the circuit for the later 3 wire so I can find a quick check for these.

Cheers,
GTM

 

[my95tsi]

I did replace the timing belt with all the other belts about 5 months ago. After driving around for about a month a noticed my alternator belt would squeel when it was raining outside so i tightened it so it wouldn't squeel anymore. If it did it too much could that be the problem?

 

[my95tsi]

So unless it's b/c my belt is too tight i basically need to replace my alternator no matter what. Damn this sucks b/c it s cold outside. It has actually been doing this for almost a year but i never cared to pay attention to it b/c i don't check my battery volatge often on my tt.

 

[my95tsi]

Ok this is my last post i promise. The volatge also reads 14.0-14.2 during the first 20-30 mintues of driving then starts to drop once the car is fully warmed.

 

[GTM]

Originally posted by my95tsi
Ok this is my last post i promise. The volatge also reads 14.0-14.2 during the first 20-30 mintues of driving then starts to drop once the car is fully warmed.

Actually you can re-edit your post for up to 1440(?) min after you have submitted it rather than having 3 posts in a row.

...................

There is no relationship between the belt being too tight and it not charging.

I would suggest if there is some place that offers free diagnosis of you charging system you should have it checked. If the battery is not holding the 13.2 volts then that is suspect for the Alt. is not going to respond by overcharging a bad battery. Auto Zone and Pep Boys come to mind for having free diagnosis but there may be others in your area. You can also carry in a unit and they may be able to test though one member here recently reported on a later car they did not have the equipment for the stor test book procedures stated "do not test". The procedure I gave you should take 1 min with a test light but it only tests that the circuits are good and will not tell you what the Alt. is capable of producing. It does not test for bad diodes or burned stator windings. For these you need more professional equipment or to partly remove covers to gain access to the diode pack.

Cheers,
GTM

 

[my95tsi]

I'm goign to autozone tommorow but my battery is brand new. But it's definitely no holding 13.2 volts. Do you think my battery is bad?

 

[GTM]

Originally posted by my95tsi
I'm goign to autozone tommorow but my battery is brand new. But it's definitely no holding 13.2 volts. Do you think my battery is bad?

I don't know but it's sounding like it's a good possibility. Do you have a battery charger? If so charge the battery overnight and then check the voltage. Pull the headlights on for 1 min and monitor the voltage and turn them off, record the voltage. With a specific gravity tester pop the battery caps off and check the electrolyte sg. This is a good test to tell you if the battery is NG.

With a fully charged battery and an induction ammeter pull the lights on for 1 min, turn them off, start car and check output B+, should be 35 amps.

Many years ago it was a big scam for battery makers to build their batteries to fail BEFORE the warranty would expire. This way they got you coming back into the shop to get your pro-rated battery use warranty which of course they made money on and had you hooked for another X years. I'm seeing more of this these days so I think it's on the rise again and perhaps a complaint to the BAR might just be the straw that broke the camel's back.

If you are going to continue to fix your own cars then buy an inductive ammeter... $3-$6 which would have helped, battery specific gravity tester $5-$12, good test light (continuity test light) like Snap-On makes.

Let us know what happens.

Cheers,
GTM