Battery not Charging…. Brushes bad?

[Dauner]

Hi everyone,

Car is 1989 911 Carrera 3.2, rebuilt to 3.4 by me about 2K miles ago. Need help diagnosing no charge condition. I have read quite a few threads. To cut to chase, does the pic of my brushes show them as suspect?

The detail:

• Crankshaft out rebuild by me several thousand miles ago. Car running great
• Difficult start after work one day but did start and parked in garage
• Next morning no start. Voltage on battery low 12’s
• Jumped car and car started immediately. Alternator light functioning correctly. No light when key out. Light comes on bright with ignition on. Light goes out completely when engine running.
• Checked battery voltage with engine running. Middle 10’s.
• Put battery on smart charger for 2 days til charger green light said full charge
• Car started great. Battery voltage before start was 12.7. Battery voltage with engine running was mid 13’s.
• Took car for 5 mile drive. Car ran fine. No alternator light. When got back to garage, battery voltage with engine running was low 12’s.
• Battery was new this spring from Autozone. Took battery in and they said battery is good.
• I removed tranny to chassis ground strap and cleaned although it was already very clean from my engine build process. Also removed battery ground and sanded terminal and all ground connectors, although they too were very clean. I don’t think the grounds are my issue
• Decided to pull alternator. Plan was to test at FLAPS but can’t get alternator out of fan housing. Have not tried John Walker rap on floor with shop rag cushion yet. Last thing I want to do is damage the fan shroud further (there is already a crack in one of the support vanes) only to find the alternator is fine.
• Alternator was replaced by PO with a Bosch approximately 50K miles ago, so I don’t think that’s my problem, but can’t be sure
• Removed voltage regulator as JW and others have said check the brushes. Pic below. From other pics I have seen in forums, it’s not unusual for one to be longer than another. My question is does anyone with experience know if my brushes look shot from the length in the pic. They are both obviously pushed back to set springs, but springs not compressed at all. Spring motion feels free.

So actually have a couple of questions:
1. Do my brushes look like they could potentially be the problem?
2. Is there any way to test the alternator at an auto parts store without removing it from the fan housing? I assume not from the videos I have seen.
3. Is there a way to test alternator vs. voltage regulator separately, versus the assembly

Thanks!

Mark

[Dauner]

Follow up post:

I was able to remove the alternator from the fan housing using the John Walker method. Worked great.

Took the alternator to Oreillys where they said it wouldn’t come up in their computer on how to test. Also I would need to have a pulley installed.

Went to NAPA where they said the connections on the computer screen looked different than the back of my Bosch unit. Strike 2.

Where have people successfully had their alternators tested? We have 2 rebuild companies nearby, but both said they wouldn’t be able to test for several weeks. Ugghhh.

I hate throwing parts at a problem as a troubleshooting method but maybe I should just install a new voltage regulator. Will wait to see if forum has other ideas or advice on testing the alternator.

Thx

Mark

[911obgyn]

Voltage regulator, brush assembly is cheapish. An alternator rebuild shop can check it. Look for auto electric starter rebuild shop in your area. Take the pulley parts

[T77911S]

leave it on the car and have it tested that way in the future.
its amazing what all they can test now, even the starter with it installed.

[Dauner]

Hi everyone,

Just to close out the thread, my charging issues are resolved. I ended up buying a new voltage regulator from host, installing, and cleaned up pin 13 on main engine compartment connector (blue wire). I believe the VR was root cause, but of course can’t positively confirm without A/B’ing with old and new. Prior to install, I took alternator assembly to Generator Specialty on Rice Street in Minneapolis and they tested on a really nice dedicated bench. Could see wave form, voltage, etc. showed 14.2 volts. I bought a Cigarette lighter voltmeter from Amazon, and am pretty happy with it. Pic below.

Thanks for the feedback and support.

Mark