Let me share an experimental fix to cancel the chassis variable voltage. This is the root cause of many chassis struggles.

The bottom line is the powertrain electronics is proven sensitive to voltage swings meaning variable voltage is a factor in computer chaos factor, namely ECU/TCU poor performance.

How proven... by running stable self-regulated alternator output the powertrain runs better.

Every MB chassis is wired a bit differently with individual combinations of features... read: "your mileage may vary!"

This quick experimental tip is "NOT A CURE ALL" magic for chassis in crisis. It's more of a cherry on a good cake else not recommended to experiment for zero difference!

> ALT-LIN Enhancement:

1. Disconnect Batt GND at brass stud + AUX GND (Reboot step1)
2. Unplug ALT-LIN!
3. CTEK float Batt on "AGM setting" while unplugged
4. Reconnect Batt Main/Aux (Reboot step2)
5. Set IC to display shop menu: Volt/Amp: 14.15Volts /1Amp.

You do need to reboot + float AGM.


Shop-Menu: 14.15V under 1A
Prior to using this tip I recommend you learn the steps how-to display battery vitals under your "shop menu" before starting the engine.

Doing this will let you monitor how the voltage and AMPERAGE are acting under normal operations.

-- Bosch excellent variable voltage is associated with normal voltage swings between 12.6V float and 14.9V bulk charging. Great!

-- I addition chassis issues can turn the 12.6V cycle into uncontrolled deep drain below 12.0V. This causes powertrain "Limp Modes, "X-Mas Tree" ESP/Pre-Safe warnings displays and premature battery EOL.

The easiest way about this is to disconnect ALT-LIN.. "We don't know what we dont know" so this is EXPERIMENTAL without any warranty.
It's entirely up to you to personally decide if you like factory voltage swings or experimental fixed voltage.


+++ ADDITIONAL SELF-HELP READING :
1 > Here.....

2 > Here.....

3 > Here.....

4 > Here.....


LIN disconnected from ALT

 

Do you mind posting some pictures to make the thread more colourful : ) ?

 

great idea, I can totally do that except I don't want this simple thread to be so easy it become entry level: "I did this and now my wipers don't work when the hood's opened" - So it's only for fair minded ppl like yourself.

What part do you need help with?

I don't like dumbed down: this is for ppl who like better : ALT-LIN SWITCH !


$1Ea on/off colourful switch wires included

Here we can not use "dummy solenoid" but we can cancel ECU code with On/Off switch wired in series with the LIN Line.
​​​​

 

Well, today is the second day of the disconnected alternator LIN and about 8-10 stop/start cycles, and the car seems to run smoother, shift more smoothly, and respond to accelerator input more quickly.

 

this is for your 3.5L N/A right?
Curious to see how your ALT LIN mod experience will be with the SL400

 

Correct. I too want to see the impact on the SL400. It's 22°F right now, so I may have to wait until Friday or Saturday when the weather is supposed to hit 40°F. I need to get at it from under the car. I may try removing the wheel well liner, as well.

 

Thanks so much forum member CaliBenzDriver for starting this thread and the pictures : )

 

Sweet stuff much appreciated you sharing the impressions. This is on my list now, I understand you got it unplugged easily on the NA M276 from the top but is it still possible for the M276 TT from the top?

 

That's a seriously amazing free fix isnt it??
ALL THAT just for getting regular 14V STABLE voltage !!


What does that tell us :
If STABLE VOLTAGE runs better than VARIABLE VOLTAGE ??
---> engine/tranny are detuned by variable voltage!

We would hope the stock Voltage variations had nearly no impact on performance but this proves to be the opposite:
Voltage variations directly impact the W212 M276-NA 722.9P basic driveability performance.

One can decide to preserve basic chassis performance by disabling voltage swings.

This concludes the initial voltage experimentation.


> SETUP Choices :
-- STABLE setup ---> strong performance.
-- UNSTABLE setup ---> stock experience.

> Meaning the various modules firmware automatically tune up performance based on normal stable conditions where man-made VARIATIONS ARE HANDLED POORLY.


> ALL FIXES TOGETHER:
-- We've seen that pressed pin connection benefit stable networking by being soldered.

-- We've seen that stable oil pressure benefits camshafts VVT timing and life expectancy.

-- We've seen that stable voltage benefit the whole chassis operation.

​​​​​​The combination makes the 722.9 tranny a big winner.
Fast strong smooth timely shifts.
ENJOY!


> IGNITION COILS vs. VOLTAGE:
-- One of the effect of better primary coil voltage is stronger secondary voltage sparks.

-- Ignition COPS are a step-up transformer.
the primary coil is charged with current under 12 or 14Volts and the secondary coil output is a factor greater around 25,000Volt with tall spikes.
-- Meaning improving the AWGauge of ignition coil harness should yield further improvements (if stock coils can handle it??)

-- Spark voltage impact the exact cylinders timing.
With stable boltage we get predictable timings: exactly what ECU needs to fire mixture reliably.

> UNSTABLE HEAT :
Unfortunately unstable heat control is also used as a chaos factor!
Loosely controlled heat impacts driveability.
There's more to this topic than just the mapped Tstat heater to control opening...
it is NOT failed but at least heat temperature regulation works poorly.

Stable viscosity is essential for the work of VVT and Torque Converter.
-- Why ? because when heat removal is improved (MOD-4), viscosity is improved and performance as well.

-- Interestingly engine oil MOD-4 helps the ATF temperature control !! Tranny stays consistent.
The outcome is perfect shifts with low RPM torque unavailable with overheated ATF.

I don't know yet how to fix the poor heat regulation but recognize it as an issue.

1. This can't be strictly Tstat heater...
2. This may be ECU painted-GND at firewall...
3. This may be circuit of TEMP Sensor....
4. This may be wonky LOAD mapped calculation...

I think it's the combination!
Sensor tells stories to ECU that controls Tstat opening and fan speed poorly.

Bottom line is the heat control is UNSTABLE and we know there's nothing good about that... concealed without code!

 

OK, just got done unplugging the SL400 alternator (it got to a balmy 27°F today). I will be going out in a little while to see how she drives. I will report back.

 

Here's some pics from the bottom...


Plugged in.


Unplugged.

 

Thanks a bunch! Is it the same type of connector as the oil pump solenoid? no dice getting from it on top right? If so looks like I am getting a back workout this weekend crawling down : )

 

Are you planning to put a dummy wire to cap it from dirt and debris?

 

It is so annoying getting under the car in this cold especially in Toronto haha.

I might do it this weekend too, like the 10th time I will be under there, hopefully we can disconnect it easily since we have 4matics and other things may be in the way..

 

Live in the same city and agree : ) but I have a bad back which makes it more difficult : ) wish we can do it from the top : )

 

I tried but the intercooler pipe gets in the way, I think even if we were to feel the connector from top it may be impossible to remove. May check it from the top again today to see if there is another way to get to connector.

 

I see, thanks for checking, if you do find a way to do it from the top please do let me know, thank you : )

 

thanks for this, this should help a lot.

 

At some point try and add the FLOAT + REBOOT steps for better results. These steps help the CAN network and the exact spark timing.

Personally I DID IT SEPARATELY and realized floating battery was better than without doing it. So I recommend doing it.

The chassis works better with a floated battery besides having stable 14.15V from disabled ALT-LIN. There are drop voltage in PreFuse related to battery current.
Less current, less losses: more voltage!

Meaning engine timings are EXTREMELY SENSITIVE to good voltage... GDI ECU dislike any form of yo-yo.

Enjoy your enhanced ownership.

 

No. It's a different type of connector, a little bigger. But only a single wire.

 

I should. But it's kinda protected where it is, as you can see from my pristine engine bay! Seriously, I don't think it will get dirty, but if I knew that parts to get, I would cap them off. I don't think I can get in there with a heat gun or torch and some shrink tubing.

 

I was able to on the C350, just not the SL. I guess it really depends on how much room you have in the engine bay. The connector is toward the bottom of the alternator, but facing the wheel well, away from the engine. If you have room to reach, maybe you can get it from the top. I just don't know how much room the turbo takes up on that side. I could reach and feel it from the top; I just couldn't get a screwdriver down there to pop that little gray latching clip and my thumbnail wasn't strong enough.

 

You know the passenger side wheel well may be a good shortcut.
Let me look..

 

Should have done it while crawling around under the car but got distracted by focusing on disconnecting the wire.

 

I was hoping that too, but there is a heat shield in the way as the turbo is close to the wheel well on the inside.