1979 911 CS questions

[Trevsked]

Hi all,

I am back in to porsche ownership once more (previously 928) and having just got this car have a few problems to sort. First of these is the alternator light which comes on as usual with ignition but when the car is started it glows dim on idle but gets brighter as the revs rise. I have put a voltmeter across the battery and it is in fact overcharging at 15.5 volts or more as the revs rise. I replaced the voltage regulator but this has made no difference. Any clues where to look next?

Trevor.

[tr7v8]

Assuming the earths are good then it sounds like the regulator pack on the alternator is knackered. Probably easiest to replce rather than repair, although you can buy a reg. pac seperately.

[Siggy]

What is the voltage at the battery, engine off..

Has your voltmeter been calibrated?

If not check the readings on another car to compare.

If the meter is good then its the regulator pack. I would (and have just done) replace the whole alternator rather than just the reg

[Trevsked]

Thanks for your input. i replaced the voltage regulator that sits behind a cover on the left hand side of the engine compartment, is there another on the alternator itself then?
I will check with another meter and another car and also the standing voltage.

Trevor.

[Siggy]

Just realised yours is a SC, So it might be different to my 3.2

[tr7v8]

Thanks for your input. i replaced the voltage regulator that sits behind a cover on the left hand side of the engine compartment, is there another on the alternator itself then?
I will check with another meter and another car and also the standing voltage.

Trevor.

It might be a seperate regulator on an older car.

[Trevsked]

Seems to be going in circles here. Yes I replaced the regulator which is separate and located on the left hand side of the engine compartment behind a cover. Is ther another regulator or could it be something else?

Trevor.

[tr7v8]

Seems to be going in circles here. Yes I replaced the regulator which is separate and located on the left hand side of the engine compartment behind a cover. Is ther another regulator or could it be something else?

Trevor.

Nope if you changed the alternator regulator then there isn't another. I'd suspect an earth lead or similar.

[zola1]

This looks like a definitive test procedure from pelican (external reg type) :-

http://www.pelicanparts.com/techarticle ... eshoot.htm

as an aside the conversion to internal reg type is here :-

http://www.pelicanparts.com/catalog/ima ... h_art1.jpg

http://www.pelicanparts.com/catalog/ima ... h_art2.jpg

I would carry out a good visual inspection of the wiring/connections as Jim recomended before you replace alternator.

any q's just ask

cheers

[Trevsked]

Thanks guys,
I cant say I understood the first Pelican article but it did give me somewhere to start.
I hope to get time to have a look at it tomorrow and let you know how I get on. Not great at electrics though.

Trevor.

[zola1]

914_electric_74E.jpg

K2 (top left of diag).is the altr w\lamp, we know that the circuit is ok to reg as it lights up and glows during eng run.

C2 is the regulator, new one fitted (inspect wiring and terms for poor connections corrosion etc, if all good :-

Disconnect battery and all leads (reg & altr)... to carry out continuity tests between the 3 wires D+, DF,D-, from reg wiring (C2) and alternator (C).should be less the 1ohm on your multimeter.

I would ensure all wiring and especially the crimped eyelets at both the reg and altr are secure and free from corrosion, pay particular attention to the MAIN Battery positive between the Battery (A on the diag).......and the post B+ on the alternator this carries the charging current to the battery and over a period of time the conductor in the wiring can oxidise and cause a high resistance (nicks in the insulator poor terminal connections etc).

Reconnect the battery and test the voltage at the B+ TERM at the alter is the same as across the battery.

If all wiring (Visual) and the indivdual continuity tests show less the 1 ohm then the altr is u/s

Do you have a current clamp ?

any q's on th above please ask.

good luck

cheers

[Trevsked]

I checked the voltage at the battery without the engine running and that showed 12.5 volts and with the engine running 13.5volts (with the new regulator fitted). There has been no change in the ignition warning light (lights when ignition switched on, dim on idle and bright as revs rise). I should get a little time to check the wiring tomorrow.
Thanks to you all again, advice gratefully received.

Trevor.