minimum length of carbon brushes on alternator voltage regulator

[shogun]

is 5mm I found in the shop manual, 5mm = what stands out of the voltage regulator housing, here shown for the M30 engine. https://workshop-manuals.com/bmw/5_s...ulator_switch/
Check slip rings for wear, disassembling alternator and fine-grinding as well as polishing slip rings if necessary. Check for truth of running of slipring. Max. eccentricity for slip rings is 0.03 mm.
https://workshop-manuals.com/bmw/5_s...h_alternator)/
Disassembling and assembling Bosch alternator 90/115/150A https://workshop-manuals.com/bmw/5_s...90_115_140_a)/
Replacing ball bearing Bosch alternator https://workshop-manuals.com/bmw/5_s...h_alternator)/
Replacing diode plate Bosch alternator https://workshop-manuals.com/bmw/5_s...h_alternator)/
Electric test on Bosch alternator https://workshop-manuals.com/bmw/5_s...ch_alternator/

Checking rotor winding for breaks and shorted turns:Place test lead for resistance testing on slip rings. Alternator type
80 A = 2.8 Ω± 10%
65 A = 3.4 Ω± 10%
90 A = 2.9Ω± 10%
115 A = 2.65 Ω± 10%
140 A = 2.65 Ω± 10%

Checking rotor winding for short circuit to earth: Connect test lead for resistance test on slip ring and rotor shaft. Specified value: ∞ corresponds to display 999 k Ω
Checking stator winding for short circuit to earth:Connect test lead for resistance test on solder point and stator (winding carrier).Specified value: ∞ corresponds to display 999 kΩ

Replacing alternator belt pulley https://workshop-manuals.com/bmw/5_s...r_belt_pulley/

Replace alternator belt pulley with overrunning clutch https://workshop-manuals.com/bmw/5_s...nning_clutch)/

This shows my original Bosch regulator after 150 kkm and the new Hella voltage regulator I installed then, the old one was definitely at the end of it's lifetime , that is a regulator for 28mm slip ring.
After I installed the new voltage regulator I also got better volts shown in the OBC. Left side the old Bosch, right new Hella http://www.bimmerboard.com/members/s...%20241_131.jpg

Alternator repair DIY https://www.rangerovers.net/repairde...haltrepair.htm

[shogun]

and this happens when you install the voltage regulator not correct, copied from BB: Voltage Regulator replacement results in LOWER voltage at OBC!
Now that that's fixed I was hoping to see the fruits of my voltage regulator replacement. Previously I would get 13.5-13.9 V at the OBC test readout. While adjusting the steering box I decided to replace the voltage regulator with one supplied by Shogun (Hella 5DR 004 241-131). Now that I've had chance to drive the car I'm only getting 12.99-13.45V (even at over 1500 rpm) depending whether or not lights and auxilliary cooling fan are on! How can this be? I test fitted the new voltage regulator twice and mounting screws fit properly. I noticed that the black plastic cover would not fit perfectly flush with the new regulator and I assumed that this was because the round black metal cap on the voltage regulator is somewhat higher/thicker? I paid the shop a lot of money to come up with the O-rings on the high pressure lines(non-standard size)and they insisted on replacing the oil cannister drain hose - $500 parts and labor! I'm so frustrated - no one else I could even trust to take it to around here! What should I do?, Remove and replace voltage regulator again? I can do that without removing the high pressure lines from the block, (I think). Or should I just replace the entire alternator? (remove radiator, tensioners, alter bolts, etc.). I certainly can't afford to turn it over to that shop again, they would make a research project out of it! It's going to get cold here again and I need good charging voltage! Photos of old regulator and new box attached. 1991 E32 750i
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Battery voltage as measured at the engine room + and strut tower - terminals is 12.7. While at idle, voltage at these points is 13.5V-13.7V. At the same time OBC test 9 says around 12.9-13.3 fluctuating occasionally as high as 13.5. Also, interior lights PULSING now + not before! Nothing to explain anything getting wet. The only change has been removal + replacement of the regulator, unless some water was used to wash off some of the oil leakage from High Pressure lines on the block. All was dry when I picked it up.
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Have you checked the alternator cable inside metal conduit between the alternator and B+ Post? While you were changing out the regulator you could have displaced the cable enough that some old insulation broke into pieces and now the copper conductor is fully exposed to the element or even shorted to the metal conduit. See my old post http://www.bimmerboard.com/forums/posts/78042/
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Yes, I am aware of common problems with this cable/conduit. Everything looks good, insulation is flexible at each end and no signs of breaks or exposed conductor. I have some more testing to do tomorrow, so I use a multimeter at each accessible end of the cable to check for resistance.
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well, the only way is to methodically test connections, did u verify the voltage drop by measuring on the cigarette lighter or so? u indicate a large enough difference that u should be able to measure across connectors till u find the place where u loose the voltage.
I seem to remember a post a while back where the poor guy went through 2 alternators before he finally found that his engine grounding strap was toast. In that case he finally found it by measuring from the alternator housing to the ground lug on the shock strut bolt. There was a voltage difference where there should be really none. what voltage is the regulator giving off on the control wire? U can measure this on pin 12 of the diagnostics connector to ground. When i had a problem with my regulator this voltage would drop to 11 or lower, correctly working it is 13.95-14.05 on my car
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Eureka! I found the problem! The pictures tell the story. The voltage regulator replacement while in the car is very difficult and you can't see how it goes in. I should have used a mirror. The first photo shows the incorrect installation and the last photo is the correct installation. Note that there are additional screw threads in the mounting surface above the actual voltage regulator. THESE ARE THE SAME SIZE DIAMETER AND THREAD PITCH + ARE EASILY CONFUSED WHEN YOU CANNOT SEE THE ALIGNMENT OF THE VOLTAGE REGULATOR! I suggest using a mirror, if possible. It is easy to mis-align the voltage regulator resulting in less brush pressure, even though it seems to fit and mounting screws seem to fasten normally. This was the cause of my low charging, checking by a local parts store showed "pulsing" of the charge. No wonder the plastic cover did not fit correctly! I thought that the replacement voltage regulator was projecting outward because of different dimensions.
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