devilinblack

Mine is not exactly the same as yours Dave, but I know that there are a variety of cases for the 130.

I talked to the shop owner and described exactly what was happening. The problem isn't that it's not charging at idle, it seems to charge just fine at idle at first, but then dies. I asked about a short on the L circuit and he thinks that could cause the described behavior. I'm going to go out and see if I can hunt down anything that would indicate that there may be an intermittent short on this wire. He also said for testing they can make it so that the alternator is self exciting, I'll just have to rev the engine a bit to get it to start and I won't get the idiot light if it stops charging for some reason. As long as I keep an eye on the voltmeter, this seems like a reasonable option to see if it's something in my battery light circuit that's frying these things.

Alan

I don't think anything you can do on L will cause a problem - grounding it will cause no initiation while putting 12v on it will definitely initiate (may not regulate very well) but as Dave confirms - no harm to the regulator. S to battery should not cause any leakage - at least not in any range you should care about for battery drain.

Running for 5 minutes and shutting down seems like a thermal protection circuit kicking in in the regulator for some reason. I'd suggest if they test it they load it reasonably and run it for 10 mins to check...

Alan

SharkSkin

When it "dies" -- does it no longer charge at any RPM, e.g. Batt. light stays on at all times?

devilinblack

It no longer charges at any RPM's. I was just out hunting for a short and I think I have at least a couple. I'm using a Fluke with the audible alarm for continuity and I connected it to the light wire and to ground, nothing. I walked away to do something else leaving it connected and after a minute with no one even near the car it started beeping. I disconnected and reconnected and it beeps intermittently. I also tested it against oil pressure sender wires and it has continuity between one of those and also (at times) with one of the battery cables that connect to the "BAT" terminal on the alternator.

I called the alternator shop and told them not to rebuild as self-exciting and I'm going to get started replacing wires as needed. Those look like 16 gauge, is that correct or would it be worth it to replace with 14?

Alan

Wire size is not that important here - very low current - just duplicate whats there - Porsche uses metric wire sizes you won't easily find in the US. Assuming its 1.0 mm^2 as on the later cars 16AWG is a fine substitute.

Well - an intermittent short there should also have been flashing your charge light - is that waht you saw? It could certainly stop the alternator from generating at low rpms (and maybe higher rpms too depending on the regulator design).

Alan

SharkSkin

Larger gauge wire can't hurt. I suggest you repeat your test with the 14-pin connector at te jump post disconnected. This will tell if it is the engine harness or if it's deeper in the system.

devilinblack

The charge light was not coming on, now that you mention it, even after it quit charging except for once. It came on once at low RPM's after I'd let it sit for a while then restarted, but it went out when i revved to 2000 RPM and stayed out. All this time the voltage never rose above 12.2.

When I disconnect the 14-pin connector I get no shorts, but it was just pointed out to me elsewhere that a circuit with a light in it will show continuity, correct? If that's the case I may not have a real short, I'm just seeing the the Light wire going through the light and to ground?

Alan

Disconnect the battery ground strap and test for continuity to ground again.

Alan

devilinblack

Battery ground has been disconnected since I removed the alternator. I disconnected the 14 pin and found no shorts across the engine harness.

Probing the other side of the 14 pin gives me the following:

1-7 24 Ohms
1-10 9 Ohms
7-10 16 Ohms

1 should be the battery light, correct? Anybody know off hand what 7 and 10 are for?

Alan

It isn't important - (oil pressure sender & temp switch) there is too much resistance for it to be a short - measure from 1 to ground instead.

Alan

devilinblack

1 to ground on the main harness side is 65 Ohms (I've also disconnected the two 25 pin connectors on the Central Warning Unit). I asked about the other pins because I've had erratic behavior with the oil level light too, but as far as I can tell the pressure gauge works correctly. One other item is that at (seemingly random) times all warning lights would come on and stay on until a restart. It's done this maybe a dozen times in the last two and a half months that I've had the car. I'm starting to suspect that all of these are related, or is that just wishful thinking?

SharkSkin

The exciter circuit goes to +12v only with the key in "run" position. With the key off there should be no continuity on that circuit either to ground or to any +12v line. If you don't already know that you should not connect your meter to anything that may have power while set to continuity/ohms -- DON'T DO IT. When I mention continuity to a +12v line I mean to say that checking continuity to any circuit that may normally have +12v -- even some ground circuits -- should only be done after making absolutely sure there is no voltage on that line. Best to just disconnect the battery any time you use that setting on the meter.

Some meters, like my Fluke, will simply blow a $7 fuse that is very hard to find if you do this. Some meters will blow a cheaper fuse. Some meters will just blow up.

devilinblack

I'll admit that my electrical knowledge is limited, but I know that sparks = bad so I've yet to attempt to test continuity with the battery connected.

SharkSkin

That's not right. Do you have the wiring diagrams? This is part 1, current track 2. If that 65 ohms does not go away when you unplug connector "O" from the CE panel, the problem is between there and the 14-pin connector. If it does, then:

If you pull connector H and the 65 Ohms goes away, the problem MAY be in that harness and/or the instrument cluster, or the CE panel. If it does not go away then the problem is in the CE panel between pins H8 and O8.

With the H harness disconnected, see if you have 65 ohms between H7 and ground, also check H8 to ground(both on the CE panel and on the harness, to be thorough).

Report your findings and we'll go on to the next step of head scratching.

Alan

Yes this is your problem - it sounds almost like you have a ~ 68ohm resistor to ground - did someone add a resistor already in the wrong place??

Can you measure what resisitance you have to the ignition switched supply from Pin 1 (say to the jump post with the ignition switch in the ignition position w/ battery still disconnected)

Alan