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Charging problem?
Posted to Technical Discussion Forum on 9/3/2013 18 Replies

Ok so I am at a loss. I have a problem with this Porsche I have been working of for about three weeks now and I'm hoping someone might have an idea or might be able to point me in a different direction. So hear we go... At idol with the a/c and all consumers off I am only getting about 12.1 to 12.2 volts at the back of the alternator. Now at first with testing the charging system with a midtronics tester, found the original alternator to be dead. So in nature after checking the battery for proper charge we replaced the alternator. Now comes the interesting part. With the new alternator (car cold) we were getting 13.5 volts at idol (consumers off) 13.4 (consumers on). After driving the car for about 20 miles we noticed the engine started to hunt at idol with lights doing all the fun stuff with low voltage. We went to retest the charging system and found the new alternator to not be putting out any voltage. Sent that one back and installed a new one. Distributor relays to us that the alternator did fail. Now with the new alternator I decided to make sure everything was good before I test drove. So with a volt meter set at the back of the alternator I watched with a hot engine and cold alternator having 13.5 volts at idol and 13.8 at 2000 rpm. After the engine ran for about 15 mins I noticed the volts beginning to drop. After about 20 mins of run time I was back to just 12.1 volts. Figuring it might just be the voltage regulator turning off due to no need of charge on the battery I started turning on all consumers to see what would happen. At idol all consumers on I had 11.8 volts at the back of the alternator. Now the kicker here is the battery light never came on while the engine was running. The light does come on with the key in both first and second position and goes out as soon as the engine cranks. I place another alternator in the car after being told by the distributor that they had a bad batch of Bousch alternators. I watch the same thing happen a third time. Now I have checked and rechecked the field wire from all ends and check for proper continuity cold and hot from all points, also checked all grounds, ground straps, connections, and the idiot bulb. I am only getting an amp pull of about 35 amps from the battery at 2000 rpm with all consumers on. So before I go and say I need another alternator does anyone have any clue to where I should go and look now.... Thanks for any help.

Anthony Padovano
Southern Star Inc
Saint Simons Island, Georgia, USA

18 Replies Received (View Replies)


car Vehicle Data

1994 Porsche 911 Carrera 2 3.6L

Engine3.6 L
Trans4-speed Automatic (Electronic)