I have a 91 vert with 158k. All of a sudden I'm getting over 16v on my battery display when I'm driving. Due to this, all my lights are getting brighter and the warning display stays on. I can get the voltage to drop some when it's at idle. Even then it's still well above 13v. I'm thinking my alternator is going bad. Anyone of you 2nd gen guys ever seen or heard of these kinds of issues? I know I need to be carerfull so I don't overload the eletrical system. Any help would be appreciated.

 

Voltage regulator in the alt is failing.

Rebuild or replace.

If you replace, consider upgrading to the 3rd gen part- higher output and it's plug-n-play on your S5 (except for the pulley).

 

Thx! I have a 20b alternator I may try 1st.

 

Yep, definately the voltage regulator. When mine went my sunroof was broken. After is started pushing 15 volts the sunroof started working again and has ever since. Even after replacing the alternator.

 

You seem to have lost the sensing wire to the small plug on the alternator. Pull the small plug offn the alternator. Key to ON. Meter on the white/blue wire. Should read batt voltage.

That plug might be off causing the problem.

 

+1 voltage regulator. You can verify with a multimeter. Even though it's pegged at 16V, I bet it's actually above 18V. Try not to drive too much until you get a new alternator; you could eventually burn out (destroy) the ECU or other electronics. The parts stores tend to sell cheap remans; good luck hunting for a good one.

Or if you must go to a big parts store, keep your warranty info and hope you get a good one the 1st time or (if unlucky) use the warranty to keep replacing short-lived alts until you do. Buy in person, don't order, to make returns easier.

Also check the plug in the back of the alternator. I think that goes to the voltage regulator; so if it's bad (loose, corroded, etc.), it'd seem like a bad voltage regulator. You might as well get your battery tested too while you're at it. It's completely unrelated to your problem, but auto parts places will test it for free.

 

Update! I just installed my 20b alternator so that took care of my problem. FYI the 20b alternators shaft was slightly larger in diameter so I couldn't refit my orginal pully. I had to use a pully off a larger american alternator (early 80's Cadillac) The 20b alternator is a 90 amp so it's a little better than what I had before. I can tell the extra amperage is helping with my window speeds and such. Now I just have to figure out what I'm going to do with my old alternator that's throwing out crazy voltage. Thx for the help guys.

 

With a whole lot of work and a 200W soldering iron (most are 20W), you can replace the voltage regulator and sell the alternator to someone else. Or more likely I'd think an alternator reman shop would want it. You'll probably get less than $20 though. They usually give you a discount of $20-$40 if you give them your old alternator when you buy a reman.