Alternator / Charging / Voltage

[dundee911]

Hi Guys, I'm new to the FORUM but been running my '76 911 [2.7lt] for over 10 years now.

I've been having charging issues. The alternator seems fine [just had it checked by a specialist] but no charge volts were making it to the battery.

Have just replaced the REGULATOR suspecting that could be the issue.

Now, the battery is receiving charging volts between 13v [on idle] up to 18v at 4000+RPM.

HOWEVER, the dash ignition light remains on and glows brighter when the revs are increased?

I have checked the feed at the regulator [from alternator] and it is reading: D+ = 13v to 23v [at high revs], DF = 8v to 12v [at high revs].

I'm worried that the higher volts [max 18v at the battery] will eventually cook the battery AND fry some of the car's circuits, wiring, components and bulbs - will it?

ALSO to note, both dash indicator lamps remain on and glow brighter with rev increases.

Any help very much appreciated.

Thanks

[93nav]

I am only an internet expert, but I would say your 18v is way to high. I use a voltmeter plugged into the cigarette lighter socket, and I don't think I ever see more that 13.4-13.6 no matter what rpm. It is lower at low rpms. I do think the cigarette lighter voltmeters may read a little low vs actual voltage. Not sure how you are measuring your volts.

On your other symptoms, I have not idea.

Pics of the car? I also have a 1976 911S.

Originally Posted by dundee911

Hi Guys, I'm new to the FORUM but been running my '76 911 [2.7lt] for over 10 years now.

I've been having charging issues. The alternator seems fine [just had it checked by a specialist] but no charge volts were making it to the battery.

Have just replaced the REGULATOR suspecting that could be the issue.

Now, the battery is receiving charging volts between 13v [on idle] up to 18v at 4000+RPM.

HOWEVER, the dash ignition light remains on and glows brighter when the revs are increased?

I have checked the feed at the regulator [from alternator] and it is reading: D+ = 13v to 23v [at high revs], DF = 8v to 12v [at high revs].

I'm worried that the higher volts [max 18v at the battery] will eventually cook the battery AND fry some of the car's circuits, wiring, components and bulbs - will it?

ALSO to note, both dash indicator lamps remain on and glow brighter with rev increases.

Any help very much appreciated.

Thanks

[911obgyn]

Yes 18v is too high!! It will boil battery!
Check all your grounds I am not sure what the regulator voltage should be. Check with an alternator rebuild shop. Do not drive for more than a couple minutes with that voltage or you may f

[911obgyn]

You may fry wiring.

[bkreigsr]

Be advised that all voltage meters are not created equally - especially the cig lighter versions.
I have three different meters in my three cars, one VDO, one SW, and one AutoMeter.
All three display (analog) different readings at full charge.
Bottom line - I only use it for a baseline monitor to see if, and when, the alternator has gone below specs.
Bill K

[spuggy]

Originally Posted by 911obgyn

You may fry wiring.

The wiring will be fine. But 18V will boil the battery, you'll be cleaning crusty/scaly grey fur off the terminals every week. And the capacitors VDO fitted in the speedo/tachometer are only rated at 15V - they really won't like 18V for long. Ask me how I know...

Anything over 14.5V at the battery terminals is not right - an older-style VR will most likely deliver 14.1V or so when working perfectly.

[Trackrash]

If there is a bad connection between the alternator and regulator, blue or black wire, or a bad ground connection it will cause your problem.