Intermitant Battery Light. Bad alternator?

[kane66]

I've lately had my battery light coming on and off lately. I had a very squeaky alternator belt for about a week during warm up. That went away but now the battery light comes on and off while driving. I check the alternator while the battery light was on on it was spinning so I know its not the belt slipping. Are these signs that my alternator is going out. Can anyone think of any other reason it would be doing that.

[jtanguay]

probably the alt... check for belt tightness and also check the connections to the alt for corrosion.  i think belt tension is the most common problem for alt/charging issues on these cars.  especially the older ones!  the v-belts like it REAL tight!  :twisted:

[vixentd]

Tightening the belt may not solve the problem.  What you need to do is
1. purchase a cheap digital meter and read the voltage of the alternator.  You should be reading 14 volts, as a fully charged battery is about 12.6 volts.
2.  Usually the problem is a worn pulley that allows the stock belt to ride down the grove and bottom out so that no matter how tight you tighten it the sides of the belt do not grip the side.  The solution is to go to one size wider on the belt if your pulley is worn.  
3. You may just have a worn belt. A new belt in the pulley grove will let you know by looking if the pulley is worn. If the new stock width belt goes almost to the bottom of the pulley then this is your problem.  
4.  If the altenator is not putting out, go to an after market vw shop or alternator and starter re builder and purchase new brushes and regulator.  $15.  It takes just a few minutes to install on the car.  Two small screws on the back of the altenator remove the brushes and regulator and slide a new one on.

[mk2diesel]

or remove the reg, clean the contacts (fingers) and re-install  ... as long as the brushes are still long enough......

[kane66]

I'm going to look into it tonight, It's still doing the intermittent thing, sometimes it works some times it doesn't. If it's spinning it should be working right (not a belt issue). I'll pull out the brushes/regulator tonight and clean it to see if thats the problem. Where about the screws I need to remove, and what should I expects when I remove the brushes and regulator, (how long should the brushes be, how many parts.. ect.). Thanks a lot for the help, I'm learning a little bit at a time, soon I will be able to moonlight as a Volkswagen Mechanic.

[mk2diesel]

back of alt  2 phillips screws ( each side of small black thing)... disconnect either battery cable first .... undo 2 screws .. twist and remove the reg ... look for 2 fingers inside the alt ( corrosion ) clean with the end of a pencil eraser ... do the same with the reg contacts ...  the brushes have a mark across them to show the MIN length ... ( pull and wiggle the brushes to stretch the brush wires to gain a bit more length ) .... carefully replace the  reg and bolt in place , re-connect the battery cable... then fire up and check the results.

[zukgod1]

If you end up with a new regulator/ brushes and don't have it actually rebuilt it can take up to 500 miles for them to seat in good. It will still charge just not as well as it will once it seats in.

[kane66]

I pulled out and cleaned the contacts on the inside of the alternator, and replaced the brushes/regulator for one off of a another alternator I have that is good. I'm still having the same problem. What I have discovered is that if I take my test light and touch it to the connector that goes to the light in the dash, and the positive on the alternator my alternator starts charging and the light on the dash turns off, and my alternator works fine after that. Does anyone know what that means. I would think that the light in the dash would be enough to excite the alternator? I don't know whats going on but I hate when things work some times and not others. I guess my next test will be to pull the alternator and try the other one to see if that changes anything. Again anything anyone can think of is appreciated.

[autoholic]

Also don't forget to check your engine to chassis ground.