Is my Alternator dying!?

[VW Scully]

Hey everyone;
As I was driving home from Sarnia tonight, I noticed my radio starting to fuzz out, my fresh air fan slowing down and my fuel gauge going down rapidly. After I finally clued in that my battery was probably dying, I turned everything off and the fuel gauge went up again confirming what I thought.

So I got home and changed the battery and now everything works again. The red Alternator warning light never came on so I'm wondering; is it dying and not 'telling me', or was my battery just finally dead?? (It was 3 or 4 years old) and yes it was dead; it's one of those AC Delcos with the green eye that tells you when it's dead; and the green eye was finally black.

Anyway, how can I test my Alternator to see if it's the culprit?? Electrical stuff really has my mystified!    Any help is appreciated as I have a car show on Sunday and want to bring the Rabbit!!!  :shock:

Oh and here's a maybe dumb question; is the alternator in a Diesel rabbit the same as a gasser??  :oops: or can I use an Alternator from a Mk2 Diesel??  :?:
Thanks  :lol:

[burn_your_money]

The easiest way is to take it to Canadian tire for a free check.  

It does sound like an alt or battery problem though although it may be a corroded wire as well

Not sure on the gas/diesel alt

[bevboyy]

Take a multimeter. Start the car. Put the multimeter probes on the postive and negative posts of your battery. Set it for DC voltage. If you get a reading of less than 13v, your alternator is on it's way out.

[saurkraut]

If its a Bosche alternator, try changing the brush assembly.  Its held on with two screws on the back of the alternator.  Its a round black thing with a white plastic two bolt flange.

Bad (worn down and short) brushes may give you a very dim light that you can only see at night.  The 13V battery terminal thing is a good check.

[rubadubdub]

remember to dab the accelerator briefly to get the alternator charging before you test it with the multimeter, as it doesnt start charging until you've done so. The red battery light on your dash should go out once youve done that, assuming the light's working. It should always light up for a bit when you start the car. If its not then something's wrong.

You can recharge those batteries with the green eye and it'll come back.

[Darth Garry]

I've had 3 sets of brushes die on me.  (I always seem to get cars around 150K miles).  They're correct above, that when the brushes go bad, you'll get a very light flicker in your battery light, only visible at night (or in a garage with the door closed).  I've never actually have an alt go bad, but the brushes go bad often.  I think they are replacable on all VW alternators (at least MK1 and II).  In MK1 motorola style you can just replace the brushes (about $8), or MKII Bosch style have the brush pack combined with the voltage regulator ($20-$30).

The voltage test is the easiest way to be sure, or take it over to the shop and have it tested for free.  That will test current as well as voltage.

Garry

[Patrick]

Scully, lots of good advice here. to summarize:
1) Put the old battery on a big battery charger with a guage. If it won't show much charge on the guage (at least 10 amps) it's toast, look no further
2) The battery by itself fully charged should give you a reading over 13 volts on a voltmeter with the car shut off not running. Not sure of the exact numbers, but the alternator charging should give a reading more like 13.8 to 14.6. If it's not reading higher with the car running, it's not charging. Might still be a connection problem as opposed to an alternator problem though.
3) Any alternator you can bolt in and have the belt line up will run that car. Watch to make sure you have the same terminals on the back if you don't want to do some re wiring.

[VW Scully]

Hey Patrick;
Thanks Upon doing the test with the Multimeter, we discovered that the Alternator WAS charging, but today coming home from the Show, the red battery light came on .
I think I am going to pull the Alternator and get it rebuilt.

It is the original Motorola and you can't just replace the brushes/voltage regulator in them but at least if I get this one rebuilt, it should fit right back on instead of switching to a Bosch with which I believe you have to change the pulley. (I think it is more expensive anyway  :oops: ).
Oh and I'm going to replace the ground strap on the battery too for good measure, since it is looking a bit worn out too.

What a pain; I have another VW Show next weekend and hope my car's ready by then!!  :shock:

[Vincent Waldon]

BTW, the red light lies like a rug... when it comes on you probably do have problems, but just because it's off doesn't mean the alternator is delivering enough current to charge the battery. It's called an "idiot light" because it's an idiot !!

A full time voltmeter is a good idea on any car... even better on a diesel that needs to get you going on those cold Canadian mornings !!

Cheap at Canadian Tire, or get the full Audi/VW set found on eBay all the time for fifty bucks or so:  volt meter, oil pressure, and oil temperature.

Vince

[Patrick]

Hey Patrick;
Thanks Upon doing the test with the Multimeter, we discovered that the Alternator WAS charging, but today coming home from the Show, the red battery light came on .
I think I am going to pull the Alternator and get it rebuilt.

It is the original Motorola and you can't just replace the brushes/voltage regulator in them but at least if I get this one rebuilt, it should fit right back on instead of switching to a Bosch with which I believe you have to change the pulley. (I think it is more expensive anyway  :oops: ).
Oh and I'm going to replace the ground strap on the battery too for good measure, since it is looking a bit worn out too.

What a pain; I have another VW Show next weekend and hope my car's ready by then!!  :shock:

You should be able to get the alternator back in a couple of days, maybe the same day if your shop of choice isn't to busy/likes you.

Where's the show? Looking for something to do on the weekend with my 5 year old. Was thinking about Joe's swapmeet in St marys, but i haven't decided totally.......

[subsonic]

Had a problem with mine.  It had something to do with the bearing starting to get play in it.  It would lose charge ability at higher rpm.  Something about it moving in the housing and getting to far from the brushes.  Well, it did do it's duty.  It was 23 years old.

[QuickTD]

If you need a quick turnaround, take your alternator to Panda Battery on Griffith road in Stratford. Peter will fix you up quick and cheap.

[Patrick]

How'd you make out? got it fixed?

[akrallysport]

BTW, the red light lies like a rug... when it comes on you probably do have problems, but just because it's off doesn't mean the alternator is delivering enough current to charge the battery. It's called an "idiot light" because it's an idiot !!

A full time voltmeter is a good idea on any car... even better on a diesel that needs to get you going on those cold Canadian mornings !!

Cheap at Canadian Tire, or get the full Audi/VW set found on eBay all the time for fifty bucks or so:  volt meter, oil pressure, and oil temperature.

Vince

I had a similar problem where the power strap between the alternator and starter would break at the alternator post. Never had the batt light appear even when driving with a dead battery from Toronto to Montreal for most of the 401. Would've never known until the tach signal wire broke as well and the entire instrument cluster flickered off.

[Vincent Waldon]

Yup, luckily diesels can run a long time without an alternator...

Vince