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Voltage Regulator Replacement

Hi all, replacing the VR on our 1983 928S, and the replacement unit came with a blue and yellow wire. The original only seemed to have a blue wire. Unsure as to where to connect the blue. Pic attached. Any help would be very much appreciated. Thank you!



Old 06-04-2018, 05:54 PM
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Voltage Regulator -

Hey Stphnsns - I've replaced a couple of failed VR's on both a 1984 and 1985 928 over the years and they have all had the Blue and Yellow leads as seen in your attached photo. These two wires connect to the spade-lugs on the Pos and Neg Diode assemblies. Here is a good discussion on replacing the VR -

Alternator for my 1983 S

What brand alternator are you using ?

Good Luck, Michael
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1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
Old 06-05-2018, 12:39 PM
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Hi Michael, thank you so much for your response. My hunch is that the "blue/yellow" wire scenario is exclusive to the Bosch units, and my car happens to have a Paris Rhone. Apparently they were fitted with either from the factory, but the majority were from Bosch. Due to this, my inclination is to just replace the entire alternator with a new/remand PR unit, as PR voltage regs alone, seem to be rather difficult to come by. Thanks again for your input and time!
Old 06-06-2018, 05:32 AM
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Petie3rd
 
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OOps bad hunch,
blue and yellow wires are going to fit the PR alternators only.
Best best refit the alternator with a bosch unit and a rear airduct housing
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Old 06-06-2018, 02:14 PM
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Thanks for the input. We actually ordered a new PR unit. Will see how that goes, and proceed accordingly.
Old 06-07-2018, 04:29 AM
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Delco Alternator -

Hey Stphnsns - Many 928 owners have had to deal with the failed/low performance Alternator issue. Personally I finally gave up on the Bosch and Paris Rhone units after being stranded on a road trip through Colorado. Prior to leaving I had made several attempts to eliminate every possible Alternator Performance weak point (real or imagined) which included :

New Bosch Alternator (Not Rebuilt) - Replaced Twice
New Huco Voltage Reg Upgrade -
New Drive Belt - Adjusted Multiple Times to Assure Correct Tension -
Rear Mounted Cooling Shroud Inspected and In place - New Air Duct Cooling Hose
Fabricated a Custom Fit Insulated Heat Shield Between Left Exhaust Manifold and Alt -
Installed Slightly Smaller Diameter Alt Pulley For Higher Performance @ Idle -
Cleaned ALL Ground Points - B+ Power Points - Battery Posts -
Engine Block to Frame Ground Strap Replaced -
Installed Digital Volt Meter to Monitor Alt Voltage at Jumper Post

Under the supervision of my wife I installed a Delco 1988 Camaro Alternator in a parking lot near Pagosa Springs. It cost less than $100 express shipped and arrived in one day. Once back in Texas I added a spacer to better align the drive pulley and firm up my install.

Here is a write up:
T/S Alternator -

There have been a number of other discussions about 928 owners using the GM Delco Alternator you might want to check on. The Price, Reliability and Performance is hard to beat.

Good Luck - Michael
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1986 930 - "Well Hung"

Last edited by JK McDonald; 06-07-2018 at 01:07 PM..
Old 06-07-2018, 01:01 PM
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Wow, this is fascinating, thanks so much for the post, Michael! I hadn't heard about this conversion, but will look into it. Its a very original and low mileage car, so you like to keep it OEM, but at the end of the day, my priority is the same as yours: not getting stranded! I will look into this. Also, for what its worth, your wife must be a better supervisor than mine -- she'd have gone shopping! Thanks again for all the input.
Old 06-07-2018, 03:34 PM
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Quote:
Originally Posted by JK McDonald View Post
There have been a number of other discussions about 928 owners using the GM Delco Alternator you might want to check on. The Price, Reliability and Performance is hard to beat.
The price is hard to beat, however the reliability may not be all it's cracked up to be. Personal knowledge (not my car) of a daily driver 928 whose local owner had to replace the Delco alternator EVERY year due to failure. Always under warranty from O'Reilly so it never cost him anything besides the time to replace. The only hypothesis that ever made sense was that the heat killed them. Every one we pulled from the car still looked perfect.


YMMV
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Old 06-07-2018, 08:20 PM
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Interesting insight, thank you. We have an OEM replacement already coming, so will likely try that first, and see what happens. The GM unit, is an interesting concept though (though I suppose the quality of the parts being turned out by GM/Delco in the mid '80s could be a topic of debate, as well). Anyway, sadly, this car is one of many in a small collection that gets driven as much as possible, but not nearly enough. Maybe 500-1000 miles a year, if we're lucky. Certainly not a DD. But, as with all mine, a nice, all original car, that is a pleasure to drive, and we'd like to keep it that way!
Old 06-08-2018, 04:25 AM
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Heat Soak -

I'm sure that the 928 alternator issue boils down to it's location and the surrounding temps it must survive in. In this environment - any brand alternator can fail at any time. The Porsche engineers added the rear cover and cooling duct to the back of the alternator in order to draw in ambient air flow far away from the heat radiated from the exhaust manifold.

One of the steps I took while still experimenting with keeping Miss Purdy powered by the stock Bosch Alternator was to build and install an insulated heat shield. The theory was to fend off some of the high temps from the exhaust manifold. It did work to lower the alternator case temps by about 20 degrees (measured with the wife's cooking temp prob) . The heat shield was installed well in advance to the final alternator failure in Colorado. (2 previous trips out west were trouble free)

Remote Mounted Voltage Regulator -

I also toyed with installing an adjustable Voltage Regulator mounted remotely on the left inner fender skirt. My theory was to remove the VR away from the claustrophobic cubby hole that the alternator was mounted in. It took a while but finally located a Volvo part that was compatible. The problem now was that the remote VR would not hold a reliable 14 volts and had to adjusted almost weekly. Perhaps there was a quality control issue - so reverted back to the case mounted Huco Regulator....

So far through two 100+ degree Texas summers the 105 Amp Delco alternator with an open back and no cooling duct has produced a rock solid 13.8 to 14.5 (depending on the load and RPM) since being installed. The ONLY mod or addition to Miss Purdy has been to leave the heat shield installed between the left exhaust manifold and the Delco alternator.

We've made several long trips without a glitch and in about a week we are heading out to Massanutten, Virginia.

Good Luck - Michael
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Last edited by JK McDonald; 06-08-2018 at 02:22 PM..
Old 06-08-2018, 01:53 PM
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Wow, thanks for all this input Michael, and best wishes for a smooth and non-eventful trip to VA!
Old 06-09-2018, 04:29 AM
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So, interesting turn of events on the alt/VR saga...We put in a brand new (PR) unit, and the orginal problem of needing to rev the engine a couple times to engage the V-reg still existed (albeit not as much revving required). Then yesterday morning, went to fire it up, and it engaged right away (yay!). drove it around a little and stopped for a while. Once I re-started the car, nothing I could do would get the VR to kick in. I drove home, thinking once I turned the car off, it'd be dead. To my surprise it re-started when I tried later. Very confusing, and would appreciate any input anyone may have! Thanks!!
Old 06-18-2018, 10:14 AM
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what is the output voltage at 1500 RPM measure at the hot post, use your multi meter

It should be 13.5 to 14.2V, lower than and it will under charge the battery this will kill it it just takes a while.
higher than and it could damage the engine computer, its not happy with voltages over 14.8v

Does the light come on the dash for low voltage?
if no light then you could have a blown warning bulb or the resistors is bad, this is on the back of the gauges.

Did you check for continuity from the blue wire where it mounts to the alternator to the 14 pin connector ?

If the alternator was left hanging on its harness instead of being supported some other way,

then the chance is good that the blue wire has sheared inside the orange sheathing about 4 inches up from the alternator.
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Last edited by Mrmerlin; 06-18-2018 at 06:05 PM..
Old 06-18-2018, 05:59 PM
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Thanks SO MUCH For this helpful reply. I do really appreciate it, and will follow your suggestions and report back, asap. Drove the car today, and it was dead on arrival (after starting fine first time) once I turned it off, so its definitely not recharging. I also do not recall ever seeing a voltage dash light, so perhaps the bulb is burned out! Looking forward to getting this solved, so again, thank you for your valuable and experienced input!
Old 06-19-2018, 05:12 AM
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