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Alternator no charge - bench test regulator?

Old 01-29-2011, 05:36 AM
dr bob
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You may want to charge the battery so that the static terminal voltage is 12.2+ before doing any more testing on the car. The fact that the alternator kicked off when you strobed the field terminal says that it's doing something. I suspect that your run-down batttery is sucking more current than the alternator can make at idle speed, hense the rising but still-low terminal voltage. A deeply-discharged or old/worn out battery can make a good alternator look bad, and extended abuse can make it actually bad. But that's a tangent discussion. Focus on restoring the field circuit wiring. The current path runs through the 14-pin connector on the fenderwall by the jump post, and it's a very low-current circuit. A little bit or corrosion there will cause the low-voltage symptom you see on the alternator end of the exciter lead, so I'd start with a thorough cleaning of the 14-pin connector; it is probably due anyway. A soft brass toothbrush is a good way to get big stuff off the connector pins and the brass sockets. Then a good contact cleaner before reassembly. If you don't have the plastic cover for that area, get one to keep the rain and car-wash water out of the electric stuff there.
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Old 01-29-2011, 07:19 PM
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Well the car still starts as strong as it did when it had a full charge, but it is worth a try. The battery was hooked up to a charger this morning so it should be good. I will do one final test tomorrow and then it's off to Advance Auto for a replacement. Maybe someday I will do a higher output swap or get a Bosch from Napa if necessary.
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Old 01-30-2011, 11:54 PM
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Same results. Brought the alternator to Advance Auto for replacement, had them test it while I was there just to be 100% sure. They also had the same results, it put out a very small amount of voltage, nowhere near enough to charge the battery let alone run accessories. Sound like the voltage regulator? So they took the alternator as a core and I should get the new on on Tuesday (no charge - lifetime warranty). Also they gave me $73 store credit for some reason...?
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Old 01-31-2011, 11:43 AM
z driver 88t
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I did a ton of searching on this a few months ago when my alternator crapped out. Similar symptoms. Would read 11-9-12V while revving engine and drop into 10.9 or so at idle.

I tried Dr Bobs suggestion as well because a bad battery can make a good alternator look bad as he says. new battery yielded same results.

The Bosch remans are a bit of a mystery. I have a Bosch reman (Bosch AL325X 90 Amp) that replaced the original Paris Rhone but its basically a Bosch reman of a Paris Rhone core. Your may still even have some of the Paris Rhone stickers or lableing on it - I think mine did.

What is unknown is whether or not it uses actual Bosch parts or if its just assembled by Bosch using Paris Rhone parts. In either case, when my old PR failed it was one of the diodes. The tester at Advance Autoparts should actually do a printout of the diagnosis that says if the failure is voltatge regulator, diodes, etc.

BTW there is another Bosch reman that fits our cars if you Google it which is the 90amp Bosch AL115X. I have not seen one but I have a hunch its the same one as the AL325X with different labeling. I'm curious which one you purchased.

In either case I swapped in a known good voltage regulator just to see if that was the issue and it wasn't - bad diode seemed to be the correct diagnosis at least on mine. Have had no issues since the install but I've talked to some people who are skeptical of the Bosch Paris Rhone remans, since no one really seems to know if the internals are really Bosch quality or just PR stuff assembled by Bosch.
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Old 01-31-2011, 12:38 PM
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Originally Posted by z driver 88t View Post
BTW there is another Bosch reman that fits our cars if you Google it which is the 90amp Bosch AL115X.
This alternator is for Audi's. I've got one. It bolts up and works just fine but does not accept the vent shroud.

BTW - The true Bosch alternators have an easily-replaced regulator and brush assembly.

To the OP - It's probably a diode or two that has failed. A trip to an auto parts store with the unit would tell you if it works.
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Old 01-31-2011, 01:03 PM
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I got a Bosch-rebuilt Bosch alternator at Advance Auto.
Was about $150. Overnight delivery from their warehouse to the local store.

Also have 2 Delco cheapo rebuilds on the 2 USA cars.
Its a patch alternative for you.
One has run since March 08, about 25K miles.
No place for air hose though.
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Old 01-31-2011, 02:14 PM
mark kibort
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broken winding is a possiblity. you suck a rock in the vent line, or if you dont have a vent line, and that gets in the alternator and takes out a winding on one of the interal rotary coils.
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Old 02-02-2011, 10:02 PM
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So far so good - getting around 14.5V with engine running
Adjusted the voltmeter reading so it is now accurate with the engine running.
Also there was an issue with the charge warning lamp (actually I broke it by mistake ) so I swapped it with the fuel reserve lamp and put an LED in the fuel reserve's spot instead. After this repair (before installing the new alt) I got 12.2v at the battery and 11.6v at the blue wire. Time to drive!

BTW I took some pics of the alt before installation, this one says Valeo on it. It is a "Worldwide Rebuild" or something. The old alt had the 928 part # on the plastic cover over the rear alt bearing, the new one doesn't.
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