Alternator Drama -

[JK McDonald]

A older retired buddy is having trouble trying to resolve a "Low Alternator Voltage" problem on his 82 928S project. He has been throwing money at this thing for well over 4 years and yet to find a permanent fix. The alternator has been replaced a couple of times and no matter the brand (rebuilt/new Bosch, Paris Rhone) the Dash Voltmeter falls below 10 volts anytime he gets stuck in summer traffic. When the alternators are cold the charging voltage is fine at +13 volts under load.

Multiple mechanics have also reportedly inspected the wiring choke points - battery cables, wiring harness, chassis to motor ground strap, 14 pin connector, etc... and verified that the voltage at the jumper post does actually read 9 - 10 volts at idle when hot. At this point he's said that his budget and frustration level has about hit it's limit and he is ready to throw in the towel.

Has any one successfully mounted one of the AC Delco Chevy CS130 or CS144 alternators on their 928 ? I've offered to help him with the installation if this is a viable option ?

So what do you think ? Michael

[harborman]

Has he replaced the main ground from the battery to the wing nut? These are known to go bad because the outside may look perfect but inside the crimped braided wire that is covered by rubber can be corroded inside. I had a voltage drop issue on my car and it was the ground cable. I actually opened up the one end and found lots of corrosion inside. $40 new cable fixed it.

[JK McDonald]

He showed me a couple of the invoices from his glove box charging him $800 - $1,000 each from 2011 (when he purchased the car) to 2016. The parts and weeks of labor have included an assortment of alternators, pod removal, plus several wiring replacements, cables, etc.... When he has complained to the mechanics about the poor alternator performance - he was told "The problem was common to this model of old Porsche and a $1,500 alternator (parts and labor) upgrade that can handle the heat MAY fix his car ?

https://928motorsports.com/parts/images/Alternators/Alternator1.jpg

I have installed new flexible cooling ducts from under the left fender and built an alternator heat shield for Miss Purdy which seems to have my 90 amp Paris Rhone doing fine. I had also looked into a remote fender well mounted VR - but after some research that idea didn't seem to provide any verifiable improvement in alternator performance.

After the last unsuccessful trip to the garage - he is thinking of just selling this project car. I agree with harborman and think there is a high resistance wiring problem that has yet to be located.

Any recommendations ?

Michael

[Mrmerlin]

I would replace the ground strap and the wires that go to the batteryt and the alternator and to the hot post ,
Contact Sean Ratts for wire harness options

[JK McDonald]

Thanks MrMerlin - He is a bit limited in his use of a computer but I'll relay all the recommendations. Although I haven't physically climbed under his car to check, I'm pretty sure all the primary wiring and cables are new. I'll also see if his cooling air ducting is still in place.

There are a couple of internet write-ups on replacing the alternator with something called a 140 amp Delco-Remy "Finned Iceberge CS-130" that certainly sounds interesting. Even the 105 amp base model CS-130 for a 1988 Camaro has evidently been installed as an upgrade with great success on the Pre-1985 Porsche 928.

https://alternatorparts.com/cs130-cs130d-series-alternators.html

Michael

[stepson]

Where are your friend and his car located, Michael?

If not close to you, maybe he's close to someone else that could help?

[JK McDonald]

Walt lives somewhere up toward Mooringsport Louisiana but I think his 928 is being stored at a garage in Shreveport. We cross paths occasionally at a fish restaurant on the Tex-La border and take the opportunity to talk about our cars. One of his friends is supposed to be a knowledgeable Porsche mechanic. Now that a ton of money has been dumped into the fuel system, his youngest son wants Walt to sell him the car. But with all the phantom electrical, instrument, warning, headlight and alternator problems he may not have deep enough pockets to take on this project-mobile.

Michael

[928 Go Go Joe]

Hi,

I installed an '88 Camaro alternator in my '84 US Spec Auto and it's great. It had a worn out Paris Rhone which still have if I decide to have it rebuilt. Just make sure to get the correct model alternator and follow the instructions in the old threads as I did. You'll need that pigtail wire connector and a few washers to fill in the gap between the alternator and block but it is an easy straight forward mod that puts out plenty of voltage and amps. You may have to ditch the belt tension adjuster but all you need is a pry bar to help get the belt properly tightened. Also the ventilation cover on the back of the new alt won't fit. It's never caused me any problem as the Delco Remy alternator has internal cooling. Give it a try and best of luck!

Joe

[JK McDonald]

Walt's last new 90 amp Bosch alternator was removed and it tested OK. Since the wiring and cables have been replaced, I think his mechanic has offered to try a smaller diameter pulley on his alternator. Does this sound like a band-aid or a reliable fix ?

There are quite a few discussions on the internet about playing around with the crank or alternator pulley for various reasons. Or should he just bite down hard and buy one of the new large capacity Mega-Thumper-Wumper 150 amp alternators.

Rather than reinventing the wheel it sounds like the CS130 Camaro alternator would probably be the best bang for the buck.

Michael

[stepson]

It would probably be best to cure the problem rather than introduce another potential issue into the mix.

Stan has already chimed in about replacing the ground strap. Has that been done yet?

[JK McDonald]

According to Walt the battery cables were new, the ground strap between the frame and block and the 14 pin connector have also been replaced. He has decided to sell the car to one of his sons and buy a Camry.

Several of the exhaust manifold gaskets along the left side of the motor were found to be leaking hot gas and is suspected to be the reason the alternator falters from the excessive heat. Perhaps the problem has been found.

Michael

[JK McDonald]

Here's the latest update on this "Low Alternator Voltage at Idle" problem. The white flag was officially waved and Walt sold the 928 to his son.

1) All the grounds, wiring and battery cables were new, reinspected and cleaned
2) The exhaust manifold gaskets were replaced
3) A new 1988 Camaro Delco CS-130 alternator rated @105 amps was installed
4) Now even in a heat soaked engine compartment with 97+ degree summer temps the alternator voltage is holding 13.2 volts at idle.

When you do a search on "928 Porsche Low Alternator Voltage" problems, it's pretty well documented as a very common issue. After repeatedly chasing many of us around the electrical system for a few laps, the solution often turns out to be that we should have just cut to the chase and gone with the CS-130 alternator. Naturally any new alternator is justified only after the basic troubleshooting steps have been completed and the grounds, cables and wiring have all been eliminated.

Hey Alan and MrMerlin - a couple of our resident expert electrical gurus - I'm sure there may be a few exceptions to the GM alternator but after reading through all the "Low Alternator Voltage" posts on Pelican and Rlists - what is your opinion ?

Michael

[stepson]

I'm verifiably not an electrical guru, but I have an acquaintance who replaced his alternator with a domestic car alternator. I could not tell you the reason, but he has had to replace that alternator each and every year due to failure.

[Big Load]

does anyone out there actually have the alternator pumping out at +14v and above??

[928gene928]

A few weeks ago, I completed the Camaro alternator conversion for the same reasons. It was inexpensive, and solved the low voltage/charging problem for me. In addition to the alternator, I also replaced the stock belt with one an inch shorter, this made tensioning the alternator easier, by allowing additional space, because the Camaro unit was smaller.