Yeah - I have the day off
And I figured out how to fix Ross's car and get work done on my 911.....
Put him underneath the 928

First off - I just did a search on Delco CS130 and it brought up plenty of good post from years past about this proceedure - In no way would I take credit, I'm probably just the last person to do this that posted
It's a delco CS130 alternator case. I believe this can be cross fit to a 1988 Chevrolet IROC 5.0l - I'm sure it fits other models as well.
The only thing mechanicaly needed to convert this alternator to the OB's is a couple of washers (spacers) behind the engine mount and in front of the alternator front ear. I did grind a bit off the adjusting bar so it could articulate a bit farther.
The only thing needed electrical wise is buying the pigtail. They also come with instructions as to which wire to connect to the exciter wire.
The pigtail will be a 3 or 4 wire pigtail with the outer wire being of a larger diameter, this we shall call the first wire - it is the second wire (the one next to it) that you need to connect as the exciter wire.
I'm kind of busy and will bring the beater in the cave and jack it up to look at the actual pin letter in awhile. Need to get a couple other cars cleared out first
If you go in with a V groove pulley - ask the parts store to change them out. It's the same shaft diameter.
I'd keep the old alternator instead of giving it back as a core, there are plenty of repair threads on the board. It can be your spare.
I haven't put a cover on mine. I haven't needed it - just one of the cooling effects of faster driving styles and keeping the oil IN the engine instead of ON it

 

Checked my blue wire at the alternator terminal and I got 2.16 volts with the key on but the engine not running. How does that sound? Jason

 

Sounds close enough to excite the alternator.


From "Electrical 928 Training" from CD's, Page 41:

Regulating voltage
Connect voltmeter to D+/61 and ground (earth).
Switch on ignition: specified value = 1.4 - 2.0 Volt
Start engine. specified value = 13.2 - 14.2 Volt


Does that help?

 

IIRC the reason the factory set the Rev limit in the 928 where they did was dictated by the maximum speed the alternator could turn at. The factory had to ensure the alternator turned fast enough at idle to cope with the high electrical loads the 928s many electrical systems could impose, yet not so fast at high revs that 1 hour on the Autobahn would lead to Alternator bearing failure.

I guess at that time P only had experience with high revving cars with small elec loads.

 

Jason,

There are two different resistors for the 928. One (original) is a different value for the original Bosch alternator. The other is an upgrade if the alternator is changed to the later type. There is a tech bulletin on this. i.e. your voltage on the exciter wire may be too high to initiate charging in you have a newer alternator.

Dennis

 

I'd love to read this tech bulletin. I have installed a new Bosch on our 1984 and have been getting voltage inconsistencies. Though I doubt it's related to the resistor, I'd like to see the definitive word on what resistor should be in place for a Bosch vs a Paris Rhone vs a Valeo.

 

84TTF,

I won't be able to scan and post it until this evening. It is in the Porsche Parts and Tech book if anyone has one handy.

Dennis

 

The resistor change (including just adding one in parallel to the bulb - earliest cars relied on the dash bulb alone) was to ensure more excitation current. Voltage is not so important as current in this case. This circuit doesn't make much difference to regulation (as long as it isn't shorted to ground) - only to the initiation of generation - once the alternator starts generating this circuit is no longer needed.

Yes Porsche seemed concerned about max rpm on the alternator so set the ratio low - but later types commonly spin much faster on modern high revving cars anyway. A larger crank pulley would be nice - but its a lot of work to change...

Alan

 

Ok guys I'm back on this PITA. I did the Chevy alternator mod, changed the gauge cluster ribbon and the front engine harness and after all that nothing has changed in my low voltage problem at the cigarette lighter. But I did more readings tonight and I think I'm on to something. Here's my readings and then I need help with a connector.

Battery car off 12.65
Ignition on engine fan running 12.20(with a slow steady drop)
Battery at Idle fan off 13.55
At cigarette lighter hit brakes 11.65
at jump post at idle 13.65
at cigarette lighter idle 13.00

Once the car was hot I believe my reading were lower(not sure about these readings I wrote them down at some point I believe once the car was hot but not sure)
Ignition on fan running 11.9
ignition on cigarette lighter 11.3

After thinking this problem is limited to the cigarette lighter circuit I remembered that the cigarette lighter didn't work when I got the car and I didn't know which wires went to it. I hooked it up with the wires that I thought went to it but the power didn't work so I found another unused (I believe switched)wire to use on a unused plug. I've tried to figure out what this plug goes to but I'm going blind trying to read the wiring diagram in my digital manual. Does anyone have a high resolution image of the wiring diagram? Anyone know what this plug goes to? The low voltage appears to be limited to this circuit that I have the cigarette lighter hooked to. Sorry for the crappy pics I used my phone. I will note that my cruise control and horns currently are not working if that makes any difference.

 

On both of mine it looks like what the sunroof switch plugs into. Or one of the two window switches. Try a continuity check between it and the sunroof motor itself.

And I'd do just what you are doing, systematically go thru and confirm / solder wires and to replace all those blue plastic splices.

 

Chris it's possible since I have no sunroof. I'm going out to look at the plug in just a minute. I'll report back in a bit.

 

Yes this is a window/sunroof/rear wiper connector (don't recall the colors)

If your windows & rear wiper work it must be the sunroof (although I wonder if the sunroof was offered on '81 models?)

The sunroof is powered by the window Regulator Relay (on with ignition & off with door opening). If its the rear wiper it is probably ignition unfused - so be careful - fix that...

Alan

 

Thanks Alan. Both windows work and so does the rear wiper. If I can ever get off this computer I'll go out and confirm it. Jason

 

I am watching this post because I just replaced my alternator with the stock one and am seeing this too. When the car is heat soaked, the gauge reads lowerthan when its cold. Last night after install it was reading 13 at idle at 9:30 pm. This morning was running just over 12 and by this afternoon was running just below 12. Heat is playing a part in mine with both alternators. Weird....

 

Latest news. Found the correct wire for the cigarette lighter plug. Did some more readings.

A/C on at idle
Cig lighter 10.72
Batt 11.99

2K RPM
Cig lighter 12.33
Batt 13.39

Battery getting weak

Ignition on Elect eng fan running
Cig lighter 10.77
Battery 11.61
Jump terminal 11.42

Tested the power coming in to the CE panel and I loose about 1/2 volt to the cig lighter.

Threw a 100 amp load tester on the batt and it dropped from 11.5 volts to 8volts. Recharging the battery for 3.5 hours and it still is drawing 10 amps from my charger I may have fried it putting the load on it. Looking like the battery may be a key to this.

Just checked the battery and it's reading 12.77 volts but the charger is still sending it 10 amps and saying it's not charged. Who knows maybe my relatively new charger is going bad.

Gonna check the battery volts in the AM and if it's still good I'm going to try the load test on it fully charged. If it fails I'm off to auto zone for a new battery. Who's got the best price on a shark battery? I'm seeing around 75.00 at auto zone, o'reilleys, and Walmart. How's that price sound?

Gonna pull the fuses and clean the contacts on the CE and replace some of the fuses too. Some look filthy. Some of the fuses look trashed.

Tha SAGA continues