alternator light and horrible noise and stopped engine
 

yup...

As the title would suggest, I am not sure where to start looking. The noise started near home, thankfully, and the rpm stopped. the noise was a horrible "something turning that doesn't want to turn" sound. The red light is on, so i assume it has something to do with alternator. all other vitals are perfect. starts for a second when key is turned then something seems to stop the engine running.

Any thoughts?

any visual clues? loose belt or fan grinding on the housing? pull off the belt and see how the alternator turns listen for noise

quit trying to start the engine. open the decklid, look.

Rtfm

you can remove the fan belt and turn the fan/alt by hand to see if that is making nosie.

if you suspect engine mechanical problems you can remove the plug and turn the engine over by hand. (you will have to put the belt back on). or with plugs out turn it over with the starter.
what ever damage, if any, is already done

you could do a leak down and compression test.

The fan belt is making the noise. Can't tell if the bearings are shot or not on the fan itself.

I'm not mechanical, so I'm trying to understand what would make a belt slip. Te fan is turning enough to burn the belt a bit.

I'm too stupid to figure it out from looking at it.

Fan belt disconnected, the engine will start and run for a short time quietly.
Alternator is the problem.
Bruce

Could be alternator bearing...mine went at red-line on the highway. Alt light came on, car shut down immediately, and upon attempts to restart, it would turn over then die out again. Don't continue trying to start as already mentioned. Do look for scratches or contact marks on fan housing.

Otherwise you have a seized engine...and that's probably not the case

the 911 fan belt is a pain in the hinney.
you need the tool that comes with the car to hold the pulley while you remove the nut.
there are a bunch of shims on there so dont drop them down into the dark hole. (down in front of the pulley).
the shims adjust the tension on the belt. more shims on the belt side of the pulley losens the belt, remove shims from the belt side to tighten. put spare shims behind washer on nut side of pulley. its a pain.

+1 Alt bearing or Regulator Brushes dislodged/broke off creating short and rattle

Remove the fan belt and spin the fan to test

+1 on alternator. Stop trying to start the engine in case I am wrong. Take this to a mechanic.

My alternator was incorrectly installed by a PO and died in a spectacularly grusome sounding way when the bearing could finally take no more. Symptoms sound a lot like yours.

It's good advice, but I'd do the once over yourself, first. Then you can speak knowledgeably with the mechanic and show that you know that your CVs don't need replacement, etc.

If the mechanic isn't a crook, then this is a good way to improve your diagnostic skills as well; if someone simply tells you there's a problem, you won't learn much on how to find it in the first place. If you miss a problem, you'll learn of what areas you need to examine more closely in the future. You can also benefit from taking the car home and attempting to identify the same problems the shop found during their inspection.

An indepedent Porsche shop should charge $100-150 for a PPI (post-purchase inspection) and, really, that's chump change for a second set of eyes detecting problems before they escalate out of control.

I am nearly certain now that it is a alternator bearing at this point. I ended to get it into my garage and ran it for about a minute. Smoke came out of the middle of the fan. Smells like burnt rubber. Fan belt is skipping.

So how do I test to see if alternator is still good? Car was running fine, no loss of battery charge it seems.

I have it in my garage, sonid prefer to try and see what I can do myself first before having it towed to my local shop.

Like said before in this thread, learning is a major goal of mine here.

Remove the fan belt.

Remove the alternator and fan assembly.

Separate Alternator from housing. Inspect.

Find some help here.

Porsche 911 Technical Articles (1965-1989) - Pelican Parts

If it has the French alternator, chances are the plastic bushing around the front (of car) bearing has surrendered. Age, heat, etc makes the plastic brittle and then break up. Bearing is likely fine as is the alternator. If you pull the alternator there is what looks like a plastic cap over the bearing. It is actually a bushing between the bearing and housing. I have an alternator this happened to which now has a brass bushing in place of the plastic in my garage. Had to make an emergency alternator replacement at track so now I have a spare.

Ahh yes, the trials of the Paris-Rhone alternator.

just remove the belt and spin the fan, no need to pull it.....yet.

if it feels bad, remove the alt, take the fan off and take it to a good shop and have the alt rebuilt.

Lots of alt bearing talk. Not looking to derail thread M9, rather to expand thinking... are alt bearing problems related excessive belt tension?

m962b, stick with it. Looking forward to see what you learn.
It's pretty easy to remove the fan pulley and move the belt aside.