924Board.org

[K-Roll931]

I need help diagnosing and resolving my alternator light issues on my 931. The light is fully lit when driving at night and a bit dimmer during the day (could be due to ambient lighting). A quick stint down the highway at speed doesn't really change the brightness of the light much.

In the last three years the battery and starter cables have been replaced, I’ve replaced the battery, installed a remanufactured alternator (75 amp I believe) and I’ve cleaned every ground point except for the one under the dash (contorting PITA, that one).

As of tonight, the battery reads 12.52v when the car is off and between 12.5-12.9V with the headlights, cooling fans and a new radio installed. I figure I’d start with replacing the regulator and go from there. Personally, I think a 75A alternator is too darn low, but it seems the only other option for these cars is a 90A and if I have to replace the alternator, I'm not sure if that'll be enough.

Any experience and/or advice is always appreciated!
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'80 931 M471 - Dolomite Gray -> Monaco Blue

[MikeJinCO]

Had a similar problem, mine was low voltage at the voltage gauge and battery going flat. The battery should be about 14+v when running. After tearing apart the dash and checking voltage, I ended up replacing the voltage regulator and the problem went away. I have never found a test for the voltage regulator.
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Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[K-Roll931]

I solved this issue after the car broke down on the side of the road last Thursday night. After replacing the voltage regulator, the alternator conked out on a drive home after class. Replaced the store brand reman alternator with a Bosch Reman 90A and everything is good now.
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'80 931 M471 - Dolomite Gray -> Monaco Blue