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Battery warning light staying on

Mark Elder

PCGB Member
Anyone any experience of fixing this?: The red dashboard light with the picture of a battery is on permanently when the car is switched OFF.

Everything was normal until I went for my first spring-drive yesterday (was a glorious day here on the west of Scotland).
Started on the button, car was superb to drive as normal. Did about 15 miles.
Parked in the garage and switched off.
As I was getting out of car I realized there was a red light on the dash (top of the clock). The battery warning light.
I switched ignition back on, the light goes out - all other lights look normal.
Started car, the battery light goes out. All lights as expected.
Switched ignition off, battery light comes back on.

I assumed maybe the battery is on it's way out and this is warning me (but I've never seen before when the battery is low).

I didn't have time to investigate so I disconnected battery out of caution.

Today I went to investigate. Multi-meter says battery has 12.48v so it's ok, could be higher, by certainly not low.
Reconnected the battery and the battery warning light came back on immediately.
Started car, light goes out. It started quickly as if battery is in good order.
Stopped car, light back on.

I found these two threads elsewhere so it looks like it's either some loom damage or a diode in the alternator:
I had the recall list checked when I bought the car it had no outstanding recalls.

Anyone here had to fix this?, if so what was the solution?


Sounds like the diode in the alternator has blown allowing back feed to the light, trouble is the alternators have been on backorder for about a year!
Thanks - it looks like Design 911 have 3rd-party alternators for 993 in stock (and also recondition ones, I assume Porsche).

Anyone experience of the 3rd party alternators? They are similar price to a reconditioned unit. Not cheap!

Reading around it looks like the diode block can be changed but other parts in the alternator likely to be well worn by now so I may as well just change it.
The Wosp versions are a higher output than the Bosch standard one fitted at factory

Try your local OPC, if there is stock you should be able to get one for under £700 + vat (it will be exchange)
Yes, Alternator £695+VAT and only £20 back on return of my old one. Had the fan cleaned up while it was off. The jockey wheel that checks for belt loss had seized up (so had that removed temporarily). Lesson = keep using the car!

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