theiceman

No idon't think it is the alternator , but I am wondering if you are losing 12v somewhere. That schematic shows everything wired together, now that we know your speedo is working we can look a little further . Do you have a meter you can check the 12 v with ?

rbuswell

My volt-ohm meter is a cheaper Radio Shack analog face. Should I get a digital or will it do?

Also, I was also looking at 970-22 and 970-23 in the Bentley and it seems to focus more on the gauges/instruments which is where I thought I might have screwed up.

rbuswell

Tried some different tests just to see if the little meter I had would do. It didn't seem to do the job as to accuracy so I bought a digital 29 range with manual and auto range capabilities so I think I'm set. About $32 which seemed pretty reasonable.

What should we be testing. Iceman?

rbuswell

There is a draw down with the car running. It tested at 11.53 V. Indicated 12.07 V with engine off.

theiceman

told ya !

theiceman

I don't think your alternator is putting out at all for some reason. the reason it drops to 11.53 is because it is running the ignition while running. The first thing I would suggest if you don't think it is the alternator is pull all the fuses that do not run the car and see if it goes up . I think there is a procedure for testing the alternator in the bently under charging sytem. try that too. you should have at least 13 volts. I would have thought hat if you had a heavy draw on your alternator it would have blown the fuse. Sounds like you could possibly have a bad alternator if you are not putting out 13.5 while running.
No matter , that is the first problem to fix. you will also need a battery charger as your engine will run down soon as the battery weakens. I iwll check the bently wile you do your alternator checks.

Peter Zimmermann

The cyclic "click" is definitely the mileage counter. I've seen that 100 times. Why the alt/reg failed while you were under the dash might be one of those truth is stranger than fiction deals. Measure your battery voltage - at idle you should show 13.3 to 13.6, at 2500 rpm you should show 13.6 to about 14.3, but it will usually be about 13.8. If your alternator died you must be sure why - no guessing here, especially since you're going to spend some bucks to have it fixed.

By the way, if you don't want to hear the click any more take the wire off the counter and tape it - nothing will be affected. You definitely have more than one thing going on, but why is the big question.
Pete

rbuswell

Gentlemen:

Again the car showed no sign of trouble at all prior to me working under the dash in the luggage compartment with the wiper change over. I hadn't driven it or even backed it out of the garage. I just finished the job and started the car and the lights started lighting up. The chances the alternator chose that exact moment to fail seems very remote to me. And I agree that the fuses should have come into play if it was a big draw down/short. All fuses are good. By the way, are there any relays that could be in play here?

I've continued to nose around and have found at least three wires that have burned, probably left over from the wiring problem supposedly "repaired" at least ten years ago by a Porsche dealer . At least the burning looked very old. A couple were to bare wire. I assume repairing those should be done regardless but it doesn't look like they were touching metal so I don't think they were shorting out, but who knows. I also suspect that finding other burned wires could be very hard to do. I searched the web and didn't find any wiring harnesses for the car but there is an outfit here in Denver that does a lot of work with harnesses so maybe they can help.

Car isn't my daily driver so I hope I won't be running the battery down. It really hasn't shown any signs of discharge at all, (over 12 V with engine off) so I don't think it's draining down much.

Peter, thanks for the insight on the mileage counter. I assume that's a reasonably available part. I didn't try checking the volts at the battery while reving the engine. I'll see if that changes anything on the multimeter readout, too.

I'm one of those "glass half full" guys, so I hope the nagging wish that I'd never done this wiper project and the frustration of chasing this problem is going to save me a much bigger headache someday. I'm going to give the fuse removal idea a try tomorrow and look at the alternator diagnostic from the Bentley book as well. I'll keep you guys posted.

theiceman

If you can remove all fuses that do not require the engine to run that would be a great start. I though those were in the back. All you really need is the fuel pump fuse and igniton, The Bently should be able to help you with that . understand what you are saying about the wiring and the cincidence, but it is , what it is .. right now your alternator is not putting out and you have to find out why.

rbuswell

Iceman:

Assumed you meant the fuses up front. Glad you mentioned that the key fuses you had in mind were in the back.

Your point is well taken. Would the draw down happen between the alternator and the battery (the alternator light and all the rest of the circuits we've been discussing) or does the juice go directly, via the regulator, to the battery. If there are no "stops" between the alternator to the battery then you're theory of alternator failure makes perfect sense. But if the path goes via the alleged short (the circuits in question) between the battery and the alternator, wouldn't the voltage at the battery still be low? Also the lights dimming under higher revs would seem to indicate the alternator is doing something and overcoming the short, to some degree.

I'll be back to you soon.

theiceman

That's the thing about electricity, it is a closed sytem , the draw could be anywhere in the cicuit and pull down the voltage. If I remember correctly there are two outputs from the alternator, one directly to the battery via the starter, the other feeds the electical systems of the car. The bently shows a pretty good picture .
Do you have an internal or external regulator ?
I felt the dlights dmming under high revs ( warning lights I hope you meant) are due to the voltage climbing from the alternator when you put more juice on , you could still have a bad diode in the alternator but lets not go there yet.

Some one else on the list also had a problem similar to yours, there alternator checked out fine but in the car it still would not work , don't know the result though.
something could definitely be drawing down the current, the only real way to know would be to disconnect the alternator from the load ( rest of the car , ) and measure the outpit, the batery would keep the rest of the car going. The problem is on there cars this is a huge pain if not impossible given the location of the allternator.

I would suggest start taking out fuses. If the car stalls , it needs that one to run and out it back if you don;t know hich ones to pop out. after that check your voltage again. You could have 2 wires shorted together somehow. I read you have to take the blower out for that mod , anything in behind that area you could have disturbed. ? have you tried rmoving the milage counter completely ? , just thinking of off the wall things ...

rbuswell

Iceman:

Had to work on the daily drivers today so the Porsche sat idle. So it goes.

My year of car should have the internal regulator; no evidence otherwise since someone would have to go retro to make it external.

Looked at the Bentley. I see your point as to the seperate battery circuit. The battery should get a full charge even if there's a draw down at the ignition switch unless a diode is bad.

Yes, I was speaking of the alternator and OXS lights dimming when revs were higher.

If I removed the alternator, can I get it tested somewhere? If so, that should eliminate it as the source of trouble, right? Maybe not if the other thread you talked about is true.

Still need to repair the burned wires. Also any ideas on testing for more bad wires?

I plan to unplug the mileage counter.

There just isn't that many wires near the blower and that's what seems so weird. The 101 project book talks about being careful about wires but none of them seemed very close. I could have moved something when I did the actual loosening and tightening of the nut on the wiper assembly I suppose.

You've been very patient and I wanted you to know I appreciate it.

theiceman

If you are up to it you can definitely get your alternator bench tested, getting it out is a real treat let me tel you. When I had mine out I had them replace the bearings in it for good measure.

Mysterytrain

There is alot of wiring behind the dash that is always hot. I'm not sure what is involved with the wiper reverse, I'm assuming its more then just repositioning the wiper arms. As stated above, I would remove the fuses one at a time and see if I could isolate the circuit that is causing this. If that doesn't help you may need to back track your work. Check out the wiring/connections to the fogs, the lighter, the rear defroster those guys are deep into the dash and one of the terminals might have popped off. It could be shorting to the painted chassis.

rbuswell

Gents:

I found at least four badly burned wires that I feel are at least a contributor to this problem. I'm going to solder in jumper wires and the best way to do that is to remove the gauges. Now the stupid question ... how do I release the red plastic inserts in the back of the gauges (which I assume are the plug-ins for the light bulbs). I'm writing down where each wire or jumper came off so I'm comfortable that I can put it all back together OK. Thanks.