911 3.2 charging low - many corrections made

[toddadale]

Here is what is going on…

13 volts charging stopped after I charged the battery; was getting drained from sitting.

Issues...

Tachometer jumps when accelerating sometimes to pegging to the end of the dial– the orange, upshift indicator light stopped working at the same time the jumping started. Other gauges are doing the same slight “jiggle” though very little. Never did this before - 11 years of ownership... Also temp gauge goes way up to a place I have only seen in in the California desert doing 90 MPH -

Cigarette digital voltmeter was always at 13.3/ 13.5 before issue (been in car for a year)
Car currently charges when running from 11.4 to 12.9 volts – mostly at 12.1 when driving
Replaced alternator/generator 2 weeks ago
Battery ground cable checked and new
Battery replaced six months ago; though tried a new battery and there was a quick delay on the starter to turn over? Solenoid? Maybe?
Replaced DME relay last week
North Hollywood Speedo is rebuilding “jumping” Tachometer – should have it back next week – said no issues, but having it rebuild anyway
Replaced coil

I am at a loss and done doing the work myself. Nothing has changed with my efforts.

[spoke]

Originally Posted by toddadale

Car currently charges when running from 11.4 to 12.9 volts – mostly at 12.1 when driving

Any voltage below 12.6 is indication that the alternator is not charging the battery. Does the GEN light come on when the key is turned to ON before you start the engine? Does the GEN light go out when the engine is started?

[Classic 911]

Ground cable between chassis and gearbox/engine?


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[Mixed76]

Originally Posted by Classic 911

Ground cable between chassis and gearbox/engine?


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Second

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[cabmandone]

Check grounds at the intake runner as well. I believe the ground for the alternator goes to the intake runner.

[cabmandone]

[Classic 911]

Originally Posted by cabmando

Check grounds at the intake runner as well. I believe the ground for the alternator goes to the intake runner.

Shouldn’t the alternator ground go to the top of the engine case?


Here seen as the thick brown cable. Make sure to clean contact points: enginecase and alternator and both cable shoes.

[brighton911]

Yes, correct that the alternator ground wire runs to the case through bolt. Your voltages say a no charge condition. You should be seeing between 14.1 - 14.6 above 2000 rpm and if the battery is fully charged, same at idle with no loads (lights etc)

[cabmandone]

Sorry if I gave bad info but G407 is the intake runner.

[toddadale]

Originally Posted by spoke

Any voltage below 12.6 is indication that the alternator is not charging the battery. Does the GEN light come on when the key is turned to ON before you start the engine? Does the GEN light go out when the engine is started?

Yes, The light acts the same before this started - Red when ignition on, off when car is started.

[toddadale]

Originally Posted by Classic 911

Ground cable between chassis and gearbox/engine?


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have not checked that - will today!

[toddadale]

Originally Posted by cabmando

Check grounds at the intake runner as well. I believe the ground for the alternator goes to the intake runner.

Thanks Nick, but what is an intake runner?

[Dan J]

Check voltage drop on positive cable from starter to battery:

https://www.google.com/search?q=voltage+drop+test&rlz=1CAKDUD_enUS831&oq=voltage+drop+test&aqs=chrome..69i57j0i512l9.12193j0j7&sourceid=chrome&ie=UTF-8#kpvalbx=_2GVOYarEBKaH9u8P_9myiAw38

I had a 3.2 car that the battery terminal was corroded inside
Drove me crazy until I found it ,changed the terminal and all was good

[cabmandone]

Originally Posted by toddadale

Thanks Nick, but what is an intake runner?

Drivers side intake manifold. You'll see several brown wires towards the rear of the car bolted to the intake.