Skunkworks

I have a 1982 928 w/ Automatic. I have replaced the alternator and the resistor. The alternator warning light comes on at startup and stays on. The engine has to be revved to 3k+ and then the alternator starts to charge. I suspect the excitor wire may have been put on the wrong terminal, but any help is greatly appreciated.

David
1982 Porsche 928 Slate Blue
Automatic

toofast928

Best thing to do Dave is cut your loses and convert the alternator to Delco.
Tony

SharkSkin

You may have connected it incorrectly. It is behaving like an alternator with the exciter wire disconnected. I have some info on the early Paris-Rhone(Now Valeo) alternator here, if that doesn't help just try a different terminal -- can't really hurt anything. Can you post a pic of the backside of the alternator?

928 Is My Favorite Time of Day

I converted to the Delco CS130 alternator in my '84 928S. Works great and charges immediately from startup. No need to rev the engine to get it to start charging. The voltmeter reading is off by - 1 volt though. The gauge can be recalibrated, but hardly worth the effort unless you need to remove the pod and instrument cluster for some other reason also. I'm pulling 13.0 volts with every conceivable electrical accessory on at idle. Tested it with a multimeter at the jump post. In your case, I'd definitely pull the alternator and check the terminals for proper hook up. It could also be a broken exciter circuit wire or a bad resistor behind the instrument panel. My previous alt was a Bosch unit that didn't have the blue wire attached and you had to rev it up to 3000 RPM's to get it charging. That was until the unit died completely. If decide to convert to the Delco, check out TooFast928's previous posts in the archives for more information. Good luck

dr bob

David--

If the dash light stays on after the alternator starts charging, you are attached to a grounded spot on the alternator rather than the exciter terminal.

My eddicat'd gess.

Skunkworks

Guys,

Thanks for the info. Especially thanks to SharkSkin with the link with diagrams. I'll work on it this weekend and let you know.

Thanks again,

David

Landseer

The exciter wire passes through the 14 Pin connector on the passenger side of engine compartment.

Its possible to have corrosion or shorts inside, depending on its condition. You might consider checking it.

Alan

This almost certainly has nothing to do with the alternator - it was probably off before (until there is an obvious problem most folks don't get to checking the voltage accurately).
As Dr bob noted - the fact his charging light come on means the wire is good and that it is connected to a ground connection (probably on the alternator).

He did say he has replaced the resistor and its a new alternator - so it should be possible to get it to work OK. Good news on getting the CS130 to work well - spounds like you are happy - did you need to make any pulley changes to install or get the Alt RPM's higher at idle - or direct install?

One thing that surprises me is that nobody seems to make internal planetary geared hub pulleys for reduction gearing of the ratio given the widespread use of this technology elsewhere - it seems to be quite reliable & relatively cheap technology can be fully sealed for long life and would seem to also enable lower belt tension & larger pulley contact areas for the same engine to alternator ratio's... why wouldn't this work and why isn't it in common usage? just cost?

You could even imagine dual ratio's with an internal transfer clutch pair (that may be going a bit far..)

Alan

dr bob

That's the ticket... An alternator with an automatic transmission. Maybe like a CVT, with charging voltage directly driving a simple DC servo coil, or a simple centrifugal governor with flyweights.

928 Is My Favorite Time of Day

Hey Alan,

As per TooFast928's conversion post, I bought a Delco CS130 from National Auto Parts for a 1988 V6 Camaro with A/C. The rebuild looked better than the one they had at Advance Auto Parts, which was a no name model. It already came with a ribbed pulley so no mods necessary on my '84 928S US Spec Auto. It required no change of the idle adjustment. Idles nice at about 800 RPM and charges great. The CS130 is a well designed piece of equipment putting out 105 amps, I believe. a newer better design than the Bosch 75 amp unit. Just my opinion, mind you...

9:28 is coming up soon. Get ready!!!

Joe

Skunkworks

Moved the excitor wire to the proper location. Alternator is working properly now.

Thanks to all for the help.

On to the next electrical gremlin...

David