Avant Sport

I've been having charging problems with my '89 200tq. A couple weeks ago I posted about broken alternator wires (2). Well, I repaired the terminal lug ends and still no charging. I noticed that I don't get a battery light with the key in the on postion. If I ground the field wire (exciter) the light comes on with key on, but no light when I hook the wire to the appropriate terminal with key on.

Voltages are the same at battery, jump post and alternator, but drops from 12.3V ( battery fully charged) to below 9.0V as engine runs and accessories run. Anti-lock off lights up and eventually battery symbol appears in auto-check.

I recently replaced the voltage regulator and today removed VR to clean "leaf-spring" type connection under the VR. Still no good.

Can I deduct that:
1. Battery light is good
2. Exciter wiring is good
3. Battery cable splice splice is good
4. My alternator is just toast?

Thanks, Tom

typ44

My first instinct is: Sounds like brushes to me.

I believe the wear limit is 7mm on the brushes.
Mine were at 6mm.

If you're handy with a soldering iron, you can replace 'em yourself after a visit to your alternator repair shop. Stop in and tell them you'd like a pair of brushes for a Bosch AL-whatever, and you'll be set back a few bucks.
If your alternator has a rear bearing sleeve, get that as well. All told, you'll be out the door paying less than 10$.

Pull battery negative, remove the regulator, remove the old brushes (watch out for the springs!).
Measure to 9mm and solder 'em in. Might be a good time to inspect the ground as well. If you plan on taking the alternator off to do this, get some electrical contact cleaner and hose off the commutator. Let it dry, reassemble.

Hope this helps!

-p

boxerfan

The key is turned on and the alternator is not turning so the battery voltage is more than the charging voltage (because there is none) and the bulb lights.

The fact the bulb does not light seems to indicate to me the battery is toast.

Whatever the case... when I am faced with this situation I replace both the alternator and battery. Done.

audiqv8

Sound as though your alternator is toasted

Fair Cape-Cape Town

Have you checked the bulb in the battery light??

Avant Sport

My brushes are fine, brand new voltage regulator with brushes, thanks.

Avant Sport

Bulb is good.

RussB

You should see a low resistance from the exciter terminal on the alternator to ground. I'll bet that yours is a high resistance. If so, replace the alternator.

If a turbo and alternator is a 90 Amp unit, I recommend upgrading from a 90 Amp alternator to a 110 Amp alternator. Search the forum for notes, since this will require replacing the alternator mounting bracket.

Here's troublehooting ideas on Bosch alternators: http://www.pelicanparts.com/techarticles/914_alternator_troubleshoot/914_alternator_troubleshoot.htm

Here's good general info (nice to see that Nikola Tesla's patent is still the controlling document, over 100 years after he dreamed of this idea!):<ul><li><a href="http://en.wikipedia.org/wiki/Alternator">http://en.wikipedia.org/wiki/Alternator</a</li></ul>

Avant Sport

all is well now.

Thanks for the input lads.