1980 911SC Targa alternator or ? electrical problem.
 

My alternator light would flash on and off at all rpm’s intermittently-the Vbelt would also chirp and the light in the car would adjust dim to bright sporadically at all ranges of rpm’s-the tachometer would also operate intermittently. The problem stopped abruptly for a couple days.

While driving the car the tachometer stopped suddenly, a mile later the car started sputtering and the engine stopped. I tried to start the car and the battery seemed like it was dead-lights would dim and couldn’t turn the motor over at all. I came back to the car a half an hour later-the car started up right away. I drove the car couple miles more-the car did the same thing again. I waited a half an hour again- it barely stated and I pushed the car couple feet home. I checked the car a week later-the car started right up.

I know this problem sounds like an alternator or regulator problem. Could it be another problem with the electrical or fuel system?

While it could be regulator\alternator related (put a meter on it and check the output), I'd be suspicious of bad grounds. Start at the battery and check the ground connections throughout.

Good luck,

Jerry M
'78 SC

I had exactly the same symptoms last year, and it ended up being the voltage regulator in my '81 SC Targa was bad. I agree that bad ground terminals can cause similar symptoms, and cause ignition system failure. I had a bad ground, and it fried the CD ignition box.http://www.pelicanparts.com/support/smileys/burn.gif I don't know if the bad ground eventually led to the regulator failure or not. Maybe some knowledgeable members can enlighten us.

This very thing happened to me a couple of months ago in my 1982 930. I had about a weeks warning before it all went pear shaped. Prior to the total failure I had been able to get the warning light to go out by increasing engine revs above ~1500 rpm, so I didn't think I was about to break down so abruptly. One dark night the rev counter suddenly stopped working and then a few hundred yards later the engine stopped completely. As I suspected, it turned out to be the voltage regulator - this was repaired and all has been well ever since. To save the inconvenience of a breakdown I would certainly recommend repairing it now and not later.

same thing here last year. new alt and reg fixed it right up.
there is a place in glendale that has the alt and reg for about 200
if you need help installing them in let me know, im in north hollywood, i can help