911 Dash Red Charging Light Please

[100702mark]

OK I have just taken delivery of my first 911 a 1978 SC Targa and working my way through the niggles. The one I'm stuck with is the red charging light. All seems to work fine when car started and driving, it extinguishes as it should. However when car is stopped, engine off, keys out it is still lit. The battery will drain in hours unless disconnected. So far having read various posts on here Ive done the following.

1) Pulled each fuse in front and back of car one by one and none cause the light to go out.
2) Pulled all relays in front fuse box and rear fuse box, none cause the light to go out. You could argue the relay for the fuel pump cause a slight change in brightness. Are there any other relays Ive missed.
3) Reading manuals etc it seemed to point to a regulator failure so I have replaced this but still the light remains on.

Previous owner says he put it away in Autumn working fine but then went it is spring and had a flat battery and since starting it the light stays on, so not apparently linked to any particular job, just being parked up and battery discharged



Please can anybody suggest where I should look next. I'm reasonably practical but please bear with me on electric terminology.

Many thanks

Mark

[210bhp]

Hi Mark

The first thing I would try are brand new batteries, not recharged ones.
If no joy, I would then check the alternator earth connector strap.
After that, if no joy, you are going to have to get a multimeter for some testing.

Regards
Mike

[KS]

Sounds like the diodes in the alternator have failed - I had this problem: charged fine when engine running but when car left overnight, battery went flat. Diodes stop the battery draining to earth via the alternator warning light by only allowing current to flow in one direction.

[210bhp]

I think Keith is right. He is good at removing the fan housing and and alternator so I would get him round to help.

Regards
Mike

[100702mark]

Thanks both, that sounds like a good starting point.

Mark

[KS]

I think Keith is right. He is good at removing the fan housing and and alternator so I would get him round to help.

Regards
Mike

On your bike!