Correct alternator Output

[911pcars]

You should be getting 14+ volts with all the electrical accessories ON. At 13.8 V, you may just need a slight adjustment of the voltage regulator or a new one (assuming the alternator diodes are okay)

BTW, on the subject of "full-fielding" the alternator for max. output; for some extra power, you could connect a switch in this circuit to open the current path to the field coils. This creates a no-charge situation and thus less drag on the drive belt. This was an old drag racing trick for a few extra. This technique is more effective with high current capacity alternators. Don't forget to close the switch otherwise you'll be stranded somewhere eventually. However, I haven't tried this on a 911 yet. I don't know if this is possible with a built-in regulator.

Sherwood

[RoninLB]

some internal reg & alt mfg will usually see a blown reg if full fielded. I can look up the hard info if wanted.. but it's not hard info on any 911 internal reg. I don't have hard info on all others or experience full fielding them..

I've only done it on external reg with a simple points ignition. Warren gave a heads-up on the possible damage to CD +.. so if I'm trapped into full fielding my car the internal reg is shot anyway.. which means buying a simple points ign coil and condensor. my car will always have points in the dizzy.

"This creates a no-charge situation and thus less drag on the drive belt. This was an old drag racing trick for a few extra. "
---- that info would sometimes come up on Hot Rod or Car Craft mags in the 60s & 70s. I got into full fielding from being responsible to getting the boat home.

[bairdc3]

I have cleaned everything Plus rebuilt alternator and still only get 13.5v with all lights on and radio.

Should I buy a new voltage regulator at this point?

Or do I go to Radio shack and get a 91 ohm 5 watt resistor and solder on the alt light connection?

[Early_S_Man]

baird,

You can use any value resistor from 68 Ohms to 91 Ohms, as long as it has a 5 watt rating. A lower value reduces the Zero-Ampere rpm value by increasing the pre-excitation current through the field windings.

Yes, I would recommend doing the resistor mod before getting another regulator.

[OldTee]

Warning. Check the red w/brown stripe wire behind the instruments and connected to one side of the alt light. Mine got hot and burned all the insulation off and shorted some other wires. Cause uncertian but I suspect a heavy current draw in one of the circuits not fused. Best way is to remove the instrument cluster with the alt light in it or from the trunk with a strong light. I am rewiring my 79SC this week.

[ruf-porsche]

Originally posted by bairdc3
I am measuring the Volts at the Cigarette lighter using a digital volt meter. http://www.cetsolar.com/voltmeter.htm

The battery was at about 11.2 volts when I returned the Refurbed Alternator to the car.

The battery seems to never take a full charge. I charged it for two days trickle charge at 2 amps only got about 12 volts, charger stated the it was never charged fully. Same thing with overnight charge at 6amp.

Battery terminals and ground to car clean and too bare metal.

If the battery is not taking a full charge it sound like one of the battery cell is bad or dead. Bring it to pep girl or the Auto bone and have them test the battery. They can determine if the battery is good or bad.

[singpilot]

There is a thread on the recent spate of Optimas going bad. Search for it. But it sounds like the batt has been replaced.

BTW, my '80SC has exactly the same voltages measured with the same VM as you now have.

[bairdc3]

Just wanted to close this one out. 14.0 volts driving down the road above 2000rpm all lights on radio and amp on.


After all was this was done.

Alternator was bad. Had Alternator rebuilt.


Cleaned all connections with small wire wheel and dremel. (Battery ground, tranny strap, starter connections, all 5 alternator connections)

Battery was bad, would not hold charge. Optima replaced no charge still under warranty.

Left 14 pin connector alone did not want to mess with that.

Did not install diode.

Last but not least bought the $29.95 external VR from our host and finally got the correct output I was looking for.

Oh and I never posted my car here she is.