My battery went dead tonight. Car wouldn't start, got a jump, she fired right up. Then after about 10 minutes of driving, everything starts going dim, then out and car stalls. Got friend to bring me another battery. Installed it, cars runs great.

So, I want to check my alternator output. I got the honking airbox out of the way and can get to the back of the alternator. My question is...I know(ie,I think) the large red wire is positive. Is the smaller blue wire negative/ground, or do I ground my neg mulitmeter lead to the frame? Or can I touch it to the alternator housing?

The Haynes manual talks about grounding the "tab" on the alternator with a screwdriver. Am I supposed to do this to test output?

What else should I be looking for/checking? No real battery issues before tonight. I did replace the alternator belt about 2 weeks ago. I'm pretty sure it's tight enough. It squealed at first, and I tightened it some more and it's quiet now. No "battery" idiot light comming on, it does come on with the key, so I know the bulb works...

Electrically challenged and confused

 

Measure the voltage from the fatter red wire & post it bolts to for positive and the alt body for negative. That little blue wire is the "exciter" wire ... we have a "2 wire" alternator which will start charging full bore as soon as you start the car up.

Measure voltage this way to start with. The grounding tab that Haynes talks about is a way to bypass the voltage regulator and the alternator will kick out all it has.

You may have a problem with your voltage regulator being shot and the brushes worn down to little nubs. I can send you a new adjustable regulator with fresh brushes for $21 with the shipping. If you have the original one from '84 it is likely shot.

 

Alternator looks to have been replaced by PO. It looks like I can pull out the regulator part w/o removing the alternator, is that possible? If so, what or how do I know if they are too worn?

Also, what are the three smaller wires hooked to the positive battery terminal?

I've done a search, and see alot of people installing your "kits". Do you have a site or list of all the "kits" or options you make up for this vehicle and the cost?

 

With a NA you can replace the voltage regulator with the alt in place. Just have situational awareness and don't force or you will snap the brushes in half.

The new brushes stick out ~ 7/16 inches from the plastic holder base.

Those extra wires on the positive battery post are Porsche's crazy wiring scheme. The heavy wire is to the starter. All the rest of the little wires are the actual wiring system to the rest of the car. Whoever designed this should be taken out and shot. LOL!

You can read about my headlight wiring kit at Danno's <a href="http://www.gururacing.net" target="_blank">http://www.gururacing.net</a> You should note that the lighting pictures that Ben took are without the wiring harness and you will get a few hundred percent more light with that. It really is pretty impressive, just ask Rennlisters that have installed. They are my best salesmen.

I don't have anything worked up on the INut for the batery cable project. The negative is $44, positive $100 and supplemental positive $54. Total $198, plus 15 shipping. These have a bunch of good features like fuses and being overbuilt to the point that they will outlast you on this planet.

 

OK I got a good mutimeter now. Digital, and one that holds the reading.

So I got it hooked up to the red wire on the alernator and the engine ground strap.

Just sitting, engine off, reads 12.51 I presume that is direct battery reading.

Start the car, get reading of 12.89 @ idle
revving to abot 2000 rpm reading of 12.91

shouldn't this be enought to charge the battery? What should it be?

 

You are way low. Want to be up in the 14 volt area at battery with motor going.

 

Yeh, I was just reading some of the "searched" posts. I did pull the reg part out. The brushes are about 1/2" long I'm guessing about 11 or 12 mm. Is there something else in side the reg unit that could fail as well?

I also assume that belt tension has no bearing on output for this test.

 

OK I have looked at alot of posts and can't seem to find one that describes getting this reg back in. The haynes is about useless as always. It seems that I need to hold the brushes down to get it to go in. Is there a trick to this?

Of course trying to get alt. off is about as big a challange. The ac to alt bolt is all but hidden/inacessable......

 

You have a NA so should be able to slip the thing back in fairly easy. Just don't jam it and snap the brushes. Well over 100 guys that bought new regulators from me have managed to put it in, just fine.

However, they probably had the alternator on the bench.

You haven't done this frequently, so you are at a disadvantage, but you can do it.