Match the #,s from the old one, Don't worry about what M-B says, If the Bosch #s match, use it!!!!

 

drags1998,
But no one can match the numbers I have, and Bosch tech support says only used the new replacement part no 1197311040. I getting mixed advice from bosch and all the part houses. Autohaus supplies that exact number that Bosch gave me, but they say it is used for only the newer 90 AMP Alternators and that it's not the correct part no. for my 100 AMP alternator. I just caledl up another MB dealership and they have a 92 SL Alternator with the same numbers as mine. He said it will pull the alternator and look at the bosch voltage regulatior number and call me back soon.
Thanks,
carltwo

 

Sorry, I misunderstood!!!!!! Those brushes look FRIED!!!!! Carefully check the armature for damage, before you go to far, It MIGHT be time to replace the Altenator as a complete unit!!!!

 

drags1998,
The armature looks good drags1998 and thank you for the thought. But here's the latest, I found 2 dealerships that actually had the exact same voltage regulator in stock. I ask if they could pull the part and give me the Bosch part number. Both did and came up with the same exact Bosch part number 1197311027. So Autohaus has those numbers and I ordered the part. So after, I called up Bosch and spoke to another Bosch tech. Gave him my V Id no, the Bosch part number on my Alternator and he again came up with the only voltage regulator that can be used for that alternator is 1197311040. I told him the conclusion I had with the 2 MB dealerships and his comment was "MB dealership's US suppliers are supplying the incorrect part to the dealerships". It would be nice to know who's correct.... The reason why I'm so anal about this, as you hear on the forums that many go threw the process of continuously replacing there alternators, could this be why, maybe?. Has anyone here replaced JUST their voltage regulator in there R129 and had NO future problems? Any thoughts....
carltwo

 

Carl sorry for not corresponding to your calls.
The storm knocked my tel lines and DSL.
So to answer your question, I think that the same regulator serves many alternators,
as long and the cut off and the start on is with in manufacturer range.
I think that it starts at -13 and cuts out at 14+.
Regards.
aam.

 

You can also bye new brushes 1 127 014 022 from Bosch cost normaly 9$ and some soldering work.
Comes with new spings and brushes and its so chep so i allways have one kit in garage, think they fit almost every bosch regulator.

 

Voltage Regulator replacement.
Well, Yesterday I received my voltage regulator from Autohaus, still concern about the numbers not being a match. So here's the steps I took:

1. Disconnect neg and pos battery cables.
2. Unloosen the belt tensioner and slip the serpentine belt to its
side.
3. Remove the 2 bolts that mount the Alternator to the engine as
I could not see any room or clearance to remove the old voltage regulator while the
alternator is connected to the engine. The bottom smaller bolt had just enough
clearance to squeeze by the fan pulley. I then was able to remove the large and
smaller wires from the rear of the Alternator and that made it possible to rotate the
Alternator around to fully and easily expose to remove the voltage regulator and
replace new. I left the Alternator in the engine compartment, as just working from
the top; I had no room to take it out of the car, as there were no jacks raising the
car. The car was sitting normal. Raising the car and going underneath was
something I wanted to avoid.
4. I clean and scuffed the old Alternator mounts, then greased
for an easier reassemble.
5. Replaced my serpentine and readjusted its tension.
6. Attach battery cables.
7. Took voltmeter test with engine off. Read 12.06. Engine on 13.09.

It's been 2 days now since the repair. No more battery light on in the instrument cluster, problem solved. Cause: Voltage Regulator.

Here's a pix below showing the slight differences between the 2 regulators.

 

Can you tell if the old one was really damaged ? or just the carbon brushes worn down ?

 

look at the difference in the brushes length between the 2 pictures, the old brushes are show completely relaeased, so that's all what is left to be compressed against the armature...

 

In his case I think that it was the brushes.
Good job Carl.
Regards.
aam.

 

Any chance this thing went bad before the brushes fully wore out?

I'm having electrical problems with the instrument cluster. Changed the battery (Napa Legend Premium 8449), and now the engine's misfiring in addition to cluster wigging out. Charged it up (trickle @ 2 amps), but problems persists.

 

Well you like to work hard.
You can check the condition of your battery and the regulator charging by hooking a multimeter.
The regulator looks good brushes are good size, now if the rest is working or not.........
I can't say.

Read with the meter you must have between 11 to 14 to keep the modules happy.
Miss firing CK you plugs, use the correct plug number.
I think I have spoke about plugs too many times. Haha.

Regards.
aam.

 

I have to work hard because this car thinks it's a primadonna.

I've got NGK BCP5ES (non-resistor, copper), which are the Bosch F8DC4 equivalent. I met a Bavarian mechanic who swore against my NGK's, but they seem fine to me. I've used NGK's on all my cars. Brand loyalty, I guess, like gasoline and motor oil....

I've measured the new battery at idle and when the altimeter is giving juice, and it's 12.6 and 14.4, give and take 0.1 or 0.2.

I have a working theory that hinges on the assumption that the green resistor in the picture should have immediate resistance. When I measured it with my multimeter, I found that the resistance started with 0 and gradually increased to 1800 Ohms in a span of ~2 seconds. That doesn't seem right.

So, if what I have is a failed resistor, then that explains why my instrument cluster acts up when I step on the accelerator hard: because the alternator wants to make more voltage when the RPM suddenly rises, but the tired resistor builds up the resistance slowly and can't limit the voltage for 2 seconds.

My theory for why I'm now having misfires after getting a new battery is that the new battery is giving a bit more power, so combined that with the extra voltage from the regulator, the cores can't handle the extra intermittent juice that the previous weak battery couldn't support.

Another odd symptom is that when the car is started cold, it misfires. After waiting for it warm up and for the RPM drop, I turn it off. Restart it immediately, and it's smooth. Step on the accelerator again, and it's misfires again.

Anyway, that's my latest working theory....

 

Update on my voltage regulator: Got a new one, and the resistor reading is the same--the same delay on the meter. On other smaller resistors I've measured, the reading is instantaneous, so I'm assuming that it's the design of these particular resistors used in these regulators.

The voltage reading from one end of the resistor to the opposite brush was about 50% higher on the new one, but it was difficult to measure because the the old regulator was hot from use, and as it cooled, the difference became only 10%. I didn't wait for it to come down to ambient, so I don't know if I could have found a difference.

So, all of this is inconclusive.

 

Here is the old thread if you want to know about voltage regulators.

Regards,
aam.

 

I have just had a battery light which was flickering at idle and off at higher revs. Now the light is on steady all the time. Car died on the side of the road with all dash lights going crazy. Tried to restart and the battery went dead, and unable to restart.

Got the car home with a borrowed battery, checked and voltage with the new battery and the car running and was only showing about 11.2 volts. Revving showed no change. Pulled the regulator off and it looked pretty old. So thanks to the forum found this thread and was able to order a new voltage regulator. In case anyone is have trouble finding one, 197311027 also goes by the box/product number 30097 which I found on amazon for $34.00

One thing I have noticed with the new regulator is the lack of resistor between the two sides which can is found on my original. Anyone think this is a problem or should I just install and see how it goes?

Thanks, Scott

'91 500SL

 

Well I put the new voltage regulator in and no joy. Bsttery light now flickers and volts are now 11.9 at the battery at idle. Perhaps there is more to it. Unless I here other ideas I will try swapping the whole alternator for a refubished one.

Do the capacitors fail often? Any checks I can do on it?

 

You must start the car with a fully charged battery.
If the battery is discharged or bad you may blow the new regulator.

Also do check for loose connectors/wiring.
Check especially the connector in the module coffin.

Right engine corner, under the plastic cover.
That is a direct positive heavy wire coming from the battery.

Regards,
aam.

 

Thanks for the help. The battery is new and fully charged.

I have checked the wires and connections in the coffin.

I think the only option now is to try the new alternator unless there are any hidden fuses or relays I could check?

Thanks again for the help aam.

Cheers, Scott

 

As far as I know there is no fuse or relays between the alternator charge line and battery.
I think it maybe cheaper to take the alternator out and have it checked at an auto. electric place.
Or, you know best.

Regards,
aam.

 

Just fitted a reburbished $134 alternator from pepboys and problem solved. 14.2volts at the battery at idle. Took less than 2.5 hours including tea break and clean up time.

 

Just fitted a reburbished $134 alternator from pepboys and problem solved. 14.2volts at the battery at idle. Took less than 2.5 hours including clean up time.

That is great.
I didn't know that there was Pep Boys in Australia.
We also have them here. Haha.
$134? That is cheap.

Regards,
aam.

 

lol, No they dont have pepboys in Australia.

I picked up the alternator at pepboys when I was in LA for business. In Australia the replacement voltage regulator was going to be $278 AUD on its own through a parts supplier. I hate to think what the sparky would have charged for a rebuild of the original. He told me he wouldnt quote until he'd seen it. I'm guessing he would have charged over $600 easy just for the rebuild as it would be impossible to find one off the shelf here in Aus.

 

The alternator can be removed from underneath a lifted car, and it's even easier... You actually don't have to take off any components to get it out...

 

Have you done it in the R129? If so then it would be nice for you tell us your trick instead of making the non helpful statement above.

I twisted my alternator every angle from underneath with no joy. I wasn't going to force it past the oil lines.

 

Many ways to skin a cat.
Yes from the bottom.

No disrespect.
But in order to remove the upper bolt.
Don't you have to remove the alternator pulley?

I don't know, but my USA has oil cooler lines.

Regards,
aam.

 

But in order to remove the upper bolt.
Don't you have to remove the alternator pulley?

Regards,
aam.

No you dont, why would you?

oh you mean to stick your hand and undo the bolt with a wrench? I personally can do it all from below, but if you have large tools or your arms are not flexible enough, you can do this small part from above...

My point is it can all be done without removing other components...

 

There you go. I couldnt get my pully off until it was on the vise and I had enough leverage. Perhaps with the pully off there would have been the room to go down..

My bolts did not require the pullys removal.

 

I dont have to remove the pulley either... as I said though, oil cooler and filter housing shape makes all the difference in the world, and if you look at EPC, you'll see how many different versions there are of the oil cooler, and they are mostly controlled by market...

BTW, removing the pulley is near impossible without an impact wrench, and fitting an full size impact gun is even more impossible without removing the shroud, and messing up the radiator itself...

 

Alternator Removal

I dont have to remove the pulley either... as I said though, oil cooler and filter housing shape makes all the difference in the world, and if you look at EPC, you'll see how many different versions there are of the oil cooler, and they are mostly controlled by market...

For the record, I also removed the alternator from the bottom. The other day the alternator on my friend's 1991 500 SL when south, making noise and the battery indicator in the cluster was blinking so I removed and replaced the alternator with the pulley on all from the bottom. The 13-mm long bolt that secures the alternator from the bottom will come off barely clearing the fan pulley assembly just as it did when I had to replaced the voltage regular on my 92 500 SL well over a year ago. Fan blade on however I did have to remove the outer and inner fan shroud and the transmission hose at the radiator end. Also because I was replacing the lower radiator hose anyway that was also removed. All this gave me enough clearance to remove the alternator from the bottom,
carltwo

 

Our cars have two kinds of alternators.

The pot type first generation and the later compact type.

The easy way to tell is that the pot has no holes/slots on top.
The compact has holes/ slots all around.

So I guess that makes for the bolt removal deference and information.

But Bayhas thanks for clarifying that.

Regards,
aam.

 

You know? I have not seen one of the old ones in years.. I forgot they even existed...

Good news the compact one is compatible with older models...

 

Summary of my experience.
Model: 1996 SL320, Bosch Alternator 0-123 510 023 (70-115A)
1. Battery Light started flickering ON/OFF then stayed permanently ON after 2 weeks.
2. Checked voltage, battery 12V, charging at 15V-15.5V, way too high. Hence alternator working, must be the voltage regulator. Pt# 009 154 8802
3. Simple instruction given in http://www.benzworld.org/forums/r129-sl-class/1470930-how-remove-alternator.html (thanks Lynn)
4. Found replacement in ebay, $35 incl S&H to Hong Kong.
5. Disconnect battery & hard/soft top computer (under backseat)
6. Remove 2 wires connecting alternator (M13 & M8 bolts)
7. Remove 3 holding screws
8. Remove black back cover (note the 3 retaining clips)
9. Replace Voltage Regulator, pay extra attention to the sprung bushes when replacing making sure that they both are in place when tighten the screws.
10. Put everything back together.
11. Now voltage is at 14V when engine is on.
12. Whole procedure took 2 hours.
Photos attached for simple illustrations.