battery or alternator ??
 

Hi all,

I know there were a few posts recently on alternator and battery topics, but I still want your advice on this :

on Christmas night, I was riding my '86 carrera on the motorway. Suddenly, I felt a loose of engine power, the car stereo would shutdown for a few seconds, then up again, and down again. The power was getting worse and I had to stop. The idle was crazy, going from 500rmp to 2500rpm. I shutdown the engine, tried to start it after a few seconds, and .. nothing, the battery was totally flat, there was not enough power to rev the engine. I had to tow the car away :-(

Well, any hint ? I guess it's either the alternator or the battery, but I could not make any further tests yet.

Hmmm.

Typically, once a car is running, it can operate without a battery if the alternator is good.

Sounds as if the alternator is going out and has drained the battery. The intermittent operation, could be a result of a drained battery and the alternator occassionally working.

Also check the fan belt.

Now that your car is home, check to see if the headlights are bright.

Just a SWAG.

As jim suggests, check your belt, if it is still there then it most likely is your alternator.
Once you have it rebuilt be sure to charge your battery before running your car , as a dead battery has been known to "fry" a freshly rebuilt alternator.
I know some of you will say balderdash to the idea that the alternator may "fry", but I have been warned of this by experienced people and feel one has nothing to lose by following this advice.

you were right, it was the alternator

thanx guys

cool you found the problem:)
as carerra posted, yes putting a new alternator (any alternator really) on a dead battery will burn out the diodes in the alternator (kills it), this happens because a dead battery is pretty much a dead short until it gets charged. when the alternator sees this heavy load it causes "overload" and the diodes are bombarded with current which then overheat and burn out.

bell
85'911 targa

My 85 carrera did the same to me last week. The warning light started to flash during idle. Put a new battery from my other car to see if the light goes off but nothing. Took the alternator to the technician and said it was charging OK. Checked all the alternator cables and they were OK. I said to the technician to check anyway the alternator because it was not charging under load. It was a bad triode in the alternator. Now is good as new. Cost for repairing? $15.00