Voltage drop issue

[wood_e]

Well after finding my alternator was bad by testing it at the store (reading 12v and under on my volt meter) I put a reman'd unit on. I tested the alt before going out of the store and it was fine.

Here are the voltages at the battery:
Running - no headlights/AC: 13.8v
Running with AC: 13.4v
Running with lights: 13.4V
Running with lights/AC: 13.1v

This was after I removed the battery in order to clean around it (there was tons of stuff in there). I cleaned the negative ground from the battery to body really well with a wire brush, and cleaned up the terminals.


I noticed on the dash that the old alt used to do this too - I just never had exact readings like this.

Anyone know what the issue could be? I assume that the voltage regulator should be keeping the car at a constant voltage regardless of the load. Are there any other grounds I should check?

[vwmeister]

Well after finding my alternator was bad by testing it at the store (reading 12v and under on my volt meter) I put a reman'd unit on. I tested the alt before going out of the store and it was fine.

Here are the voltages at the battery:
Running - no headlights/AC: 13.8v
Running with AC: 13.4v
Running with lights: 13.4V
Running with lights/AC: 13.1v

This was after I removed the battery in order to clean around it (there was tons of stuff in there). I cleaned the negative ground from the battery to body really well with a wire brush, and cleaned up the terminals.


I noticed on the dash that the old alt used to do this too - I just never had exact readings like this.

Anyone know what the issue could be? I assume that the voltage regulator should be keeping the car at a constant voltage regardless of the load. Are there any other grounds I should check?

Those figures look normal for a Euro car. Voltages typically go down with increased loads. It took me a while to get use to them too. If it were a domestic then I would begin to look for problems as they run 14.5V to almost 15V all the time. Are you having problems with the battery going down/dead? Parasitic draw should not exceed 400 mV

[wood_e]

Nothing wrong with starting at all - my battery seems to be OK.

I guess I'm just used to having 14v after having my Taurus SHO...

Maybe I'm overreacting... except I sure don't want to have to replace that alternator again....

[vwmeister]

Nothing wrong with starting at all - my battery seems to be OK.

I guess I'm just used to having 14v after having my Taurus SHO...

Maybe I'm overreacting... except I sure don't want to have to replace that alternator again....

As long as your battery light comes on with the key in the "run" position and goes off after starting your car all is fine. :tu:

[Loccusst]

You could always have the bat tested. It sounds like everything is fine though. On the new VW the voltage actually runs at 14.5 volts. I love it because of all the electrical junk I put on my car.

[wood_e]

The battery was replaced in 2004 - I do have a battery tester so I might give that a shot....

[OrangeDUB]

Well, you COULD beef up the alt cable that runs to the battery, not sure if that would help but it's one thing that may help... Also I have to agree that those #'s look ok to me.

Hey since you probably have a perfectly good working alternator, you could probably polish it up and sell it on the tex?

[Loccusst]

Good idea, might as well get some money back out of the whole thing.

[wood_e]

Well the old alt I had WAS indeedd bad...

[OrangeDUB]

Well the old alt I had WAS indeedd bad...

Gotcha.

[wood_e]

Ok well tonight those numbers got worse...

Idle - 12.7v
AC on 12.4
Lights on 12.4
Lights + AC - 12.2-12.3...

Not good... I don't think its my battery as I have no trouble starting...

[Loccusst]

Interesting....get the bat tested, and the rest of the charging system.

[wood_e]

I'm going to check it out tomorrow after work - 90 miles round trip though. I hope I can make it. I'm charging the battery tonight so we'll see what happens.

[wood_e]

UPDATE!

I checked the poser at the alternator

Large post: 13.8v when running
Small post: 14v running

WTF? wiring issue?

[wood_e]

http://i2.photobucket.com/albums/y3/woojo/batterycable.jpg

^ could that wire be the culprir

[wood_e]

Battery + to alt + while running = 1.66v

plus the alt post was HOT so theres resistance there - time for a new terminal

[wood_e]

Bingo - replaced the alt to battery cable and converted to a marine battery terminal

Idle - 13.8v
AC on 13.67v
Lights on 13.67v
Lights + AC - 13.5v

[turboA4]

YAAAAAAYYYY!!!!! good job!!!