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Discussion Starter · #1 ·
Just bought this '87 16V Scirocco with a bad alternator, the battery light would come on at about any RPM above 3K, I think it was still charging a little bit though since it made it 120 miles on one battery, and 60 of those miles was with the headlights on. Replaced brushes, no go.
Got an alternator I know to be good off a 16V Passat, installed, no more battery light! YAY! But now the car dies even faster... With my multimeter I get about 11.5V from the battery with the car off, and about 11.5V with the engine running... hmmmm. Tested continuity between the blue wire terminal on the alternator and the connector for the blue wire next to the battery... and it's good. Thats all I know so far.
Last bit of info here- when I removed the alternator from the Passat I accidentally forgot to disconnect the battery, and during removal fumbled and made contact with my wrench between the big positive terminal and the case. Big spark! Guessing that could be why it isn't charging now.. but why no battery light? Thanks in advance for any info at all!
-Rob
edit: just noticed that with the car off and the ignition on, the OXS light is on and the oil light blinks... but the batt light isn't on. This normal?



Modified by robw_z at 11:15 PM 2-14-2004
 

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Re: Alt not charging, but no battery light. Help!? (robw_z)

" just noticed that with the car off and the ignition on, the OXS light is on and the oil light blinks... but the batt light isn't on. This normal"
it's normal but the alt LED should be on when first starting engine and go out when revving the engine. Your LED circuit might be bad even if the wire tests OK between the alt to the connector. you probably have to pull the cluster connector and check for continuity there. Start the car and touch the blue wire to the positive batt pole and then measure the alt ouput
 

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Discussion Starter · #3 ·
Re: Alt not charging, but no battery light. Help!? (robw_z)

Jumped the blue wire to positive terminal, alternator still does not charge. Guess it's just a bad alt?
-Rob
 

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from myt personal exp, don't worry about hte alt light, u can have adead alternator and the light doesjn't come on, three 16v cars here to know that. but u can try putting in a new bosch voltage regualtor, bought 15$ it fixed one of my ailing alternators
 

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Re: (austin neuschafer)

Quote, originally posted by austin neuschafer »
from myt personal exp, don't worry about hte alt light, u can have adead alternator and the light doesjn't come on, three 16v cars here to know that. but u can try putting in a new bosch voltage regualtor, bought 15$ it fixed one of my ailing alternators

no...worry about the light. its not lying to you. the same wire that makes you have an idiot light is also the exciter wire, which tells the alt to spit out a charge. your light should come on with the ign on.
 

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Discussion Starter · #6 ·
Re: Alt not charging, but no battery light. Help!? (robw_z)

Any more input? Still confused here...
-Rob
 

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Re: (adidas_mc)

Quote, originally posted by adidas_mc »
no...worry about the light. its not lying to you. the same wire that makes you have an idiot light is also the exciter wire, which tells the alt to spit out a charge. your light should come on with the ign on.

Absolutely correct. The blue wire provides the exciter voltage to the fields of the alternator. Without it, it won't work. Since it runs through the idiot light on the dash and that doesn't work, I would start there.
 

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Re: (Elwood)

Take the alternator to a shop and have it bench tested. Several places do it for free (Checker and NAPA). That will tell you if the alternator is bad. Next, check your wire for corrosion or breaks. From what I understand, if the blue wire is not connected, your alternator will give you no love.
11.5 with the car off is a little low. You should be over 12.
 

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Re: (wagenbob)

i think it would be more efficient if he checked the wires first, then removed it to have it tested. but with the dash light not coming on, you should first focus on getting that squared away. find where the connection is broken.
 

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Re: (adidas_mc)

yeah same thing happened to me. My Battery light would not come on before starting the car. With a new alt and battery I was still getting stuck. I thought I had something draining the battery while the car was off but it wasn't the case..... If you do a lot of stop and go driving you will really notice it because your alt will "go to sleep" if the exciter circuit is not working.
I actually had to pull the cluster and resolder some of the joints where the battery led socket was attached to the board
Resoldered it and the battery light worked again and have not had to beg for a boost since!
 

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Discussion Starter · #11 ·
Re: Alt not charging, but no battery light. Help!? (robw_z)

OK, I switched back to the old alternator and then the light worked again... so I decided to check the brushes, even though the PO said he had just replaced them. They were VERY VERY BAD. Swapped in the brushes from the other alt, and now all is fine and dandy in my little VW charging world.
-Rob
 
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