Sharing..........

My indie requested my help to troubleshoot an ML400 it is W166.056 chassis of 2015.....for its air-cond issue.
My indie is not into HVAC.

I wont be posting in ML/GLE forum, I am here to explain not about the car, but of a Fake Denso compressor and what happened to the N22/7 AAC ( HVAC computer) in response.

The back story is as follows :
01. New customer this ML400 guy is, reccomended by another long time client.
02. The car seems to be recently puchased, high chance it is the case.
03. Client complained the HVAC is poor/hot unless at highway speed.
04. Client bought a new compressor from local on-line store, and asked my indie to install the compressor.

05. Indie installed compressor and he can't even charge R134A into the system LP port, and the HVAC computer also went banana.
Went banana like this : All display on the unit does not show fan speed bar or temperature.
Only A/C-Rest button blinking and the blower is running at 60%ish speed. Pressing any button has no effect. Radiator fan is normal, not like full jet speed running.

This photo is key out. So car is dead.

The auto light is lighted too while the A/C-Rest is blinking the moment key is in IGNITION ON, engine OFF or when engine running.






So I ran a xentry scan and do pressure reading on LP and HP port engine OFF and then engine ON.
While car engine is still hot, which should be at least 60C metal temperature of HVAC components in the car and thus I will get over 200PSI for sure at both LP and HP.
But I got only 73 PSI.

Note the time 10:18AM - ENGINE OFF




Engine ON, HVAC as is, blinking A/C-Rest and blower keem humming. No indicator of temperature and speed of blower ( bar graph ).
AUTO is ON. It does not react to any button pressing. Must be cooling fan cooling condenser, thus R134A pressure drop a bit by like -3 psi.



I am not suprised R134A pressure this low, because my indie told me he can't charge it, HVAC does not work.
I then recovered about only 96 grams of UNKNOWN shi-et. Does not smell like R134A. Smell like sovent.
This car is a 1,050 grams fill level.






This ML400 uses Code 580 el-cheapo aircond like my E400, single Evap.
Code 581 is the higher end HVAC system.
Code 582 is with rear evap, so two EVAPs
Wow, single EVAP like mine, yet 1,050 grams vs 590 grams R134A mine is. The EVAP must be like double size of mine I guess....whatever.

F-ing dirty car with the MB in-famous VVT mini window leak. I feel sad when looking at dirty engine bay.
Engine is the same family as mine M276.821 ,3.0 TT. mine is M276.820
4.9 BAR x 14.5 = 71 PSI.


Above in red, the power consumption of A9 Ref compressor at 127,996mA ( 127.9 amps ) must be some sort of maximum numeric number in the memory , like out of range I guess.






So I boroscope-ded the compressor label.


WTF the label of a new compressor can have the print wiped out ? They print with home use inkjet printer ?
I still can see it is A 000 830 98 00 P/N.


-----


A dangerous positive jumper block ( F32 fuse block ) location !!
The hood gas strut is negative/ground !!! So I taped the gas strut. I also placed plastic board on metal body closest to this F32.

.

.



.



Need good power supply, the condition of the HVAC blower at 82% stuck ON is needing 32 amps of battery maintainer.

Later on, I did a few Xentry scan again to see what speed/power is the interior blower doing ? Thus I know it is 82%



---------

So I tried jacking up this fat ugly car with my Quick Jack to see the AC compressor, blo-ody hell, my QJ is 7cm too short for ML400
I need to see the compressor with my own eyes.

My wheel stand came to the rescue !!!!

.



ML400 has massive suspension travel, must be. I think I can put my head inside the wheel fender well. Tire is only 3cm off the ground.




UNDER THE CAN FINALLY..........
I wiped clean any dirt on the compressor label using Simple Green which is so mild and non offensive....WTF, the label is even loosing more print
Oh oh....this is a guarantee FAKE DENSO !!!!

Made in GEMANY ha ha ha GERMANY you F-ck bast-ardz counterfeiter !!!! I feel sorry for my Indie who got stuck with this kind of SHI-ET



----------------------

So I tried compressor actuation, but using bulbs as load and not the AC compressor control valve solenoid.
It works, no DTC of Short circuit to ground 91EB11
I know Denso limit is 1 amp only for Control Valve. 950mA is the highest I seen on my own car.



I called my Indie to bring the OLD compressor. I want to see its solenoid valve, thus I posted about it here : https://mbworld.org/forums/e-class-w...-how-test.html
At the point in time I do not know yet if this YESTERDAY's installed compressor was choosen wrong and has no diode where perhaps ML400 need one with diode.
I ran the P/N check for this specific ML400 by VIN and the P/N is different to what is installed ( as if this Denso compressor is genuine )

It should be using A 000 830 52 00 and not A 000 830 98 00 ( let's forget the fake Denso compresor for now ).



So I checked with EPC, what car uses A 000 830 98 00 ?



So, W166.856 uses this A 000 830 98 00 and is also M276.821 engine like ML400.



Ok, at least I know the P/N use by fake Denso is a real MB P/N

----------------

When the used/original compressor arrived.... I ran P/N check, and it is NOT the true compressor for ML400, but it appeared as genuine Denso.
WTF is going on......

The previous compressor on the car.




Its official MB P/N is




Compressor A 002 230 31 11 is for older M272 engined W212.
W212.056 is E350 using M272. Also for W218, W204 , W207 and W172 ( SLK )....meaning not a "big" car with 1,050 grams R134A I am assuming.


Holy Cow, what an historical AC compressor replacement mess !!!! At least it is a genuine Denso.
So I took out the oldie compressor Control Valve to do actuation test.


.





I filled up the HVAC system with nitrogen at 135psi or near 10 BAR. Hoping to fool the refrigerant pressure sensor, and stop making low pressure DTC.



.

Xentry actuation test for compressor Control Valve





Yellow Fluke is VOLT, DC and red UNI-T is % duty cycle
Note , since the N22/7 is pulsing PWM voltage, regular DMM will read like below, if using Scope it will read pulsing 12V as 12V.



.


.


.




100%




Will continue......................

 

So, now that I have a baseline on how an original/genuine Denso control valve power consumption is from 10% to 100% duty, I try again on the fake DENSO compressor.

I prepared diodes, emergency on-line shopping, 3 hours arrival. At this point in time I am still thinking what if the fake Denso is supposed to have a diode built-in at the control valve but did NOT have it.
I bought 1.5 amp, 2.0 amp and 3.0 amp version.



Soldered the diode and hose it as protection from bending or short to ground.



Go under the car.... and install jumper cable set.
ML400 is VERY easy to reach the compressor connector, unlike my E400.



I was doing vacuuming at this time. My hope were still high that this is all about Diode only.



.
TEST IN PROGRESS - FAKE DENSO


.



.




.



.


.

.



Wow, I hope the N22/7 computer did not go partially bad because of the f-king fake Denso control valve being power hungry.
Fake denso controller valve is 11 ohms when measured for its coil resistance.
Genuine Denso controller valve is 11.2 ohms, thus by Ohms law the genuine one did follow Ohms law, it consumed at maximum power when I use 12V power supply not PWM , it is 1.02 amps.

I think N22/7 has amperage maps inside its memory that at 20% duty, it should never exceed 500Ma or something, genuine Denso valve consumed only 152mA at 20% duty cycle.
Thus N22/7 did not wait till exceeding 1 amp or 1,000mA and produced the DTC immediately....maybe .


===================


I am not happy with what happened. I want to learn more of N22/7 behaviour, albeit different car to mine, perhaps it shares the same logic of operation and safety parameter.
So I tested my E400 .


.


.


.



....... No CAN'T DO.

Is it because ML400 is using different type of N22/7 software and/or hardware ?....where it can do AC control valve actuation even with ENGINE OFF ?
Or ML400 N22/7 had gone partially bad ?
I don't know.

Tomorrow a new but I think 99% is also FAKE Denso with supposedly correct P/N will be given to me.
Let see what happen tomorrow.

---------------------

1 more thing.

Both my E400 and ML400, can not command ( operate/actuate) radiator fan M4/7 to activate when engine is not running.
But ML400 N22/7 shows fan %...LOL.......... but fan is dead.




.





Till tomorrow guys............

 

I learnt something new no WIS shed a light on... I am rather comforted.
While I am pissed doing work on a fake Denso compressor, the evil has a good side too.

A claimed genuine MB-Denso was sent to me by owner to my Indie and two of my Indie staff brought it over to my house, Sunday morning....hhhmmmmmm FAKE DENSO again !!!!


The box has NIL MB labeling, which I am so familiar. Because I can track the barcode on it.

Never mind, swallow the pain pill for learning sake.


Let's test the control valve electrical behaviour

.




.




.




.





At least the 100% amperage is under 1,000mA. So far OKEY.


My indie staff , 2 person, installed the compressor.
I did the oil balancing. The least I could do to improve the life of this fake compressor. Is to replace the oil with Denso ND-8 genuine.

It came with non genuine Denso oil for sure. Denso ND-8 oil is basically so clear so nice, not yellow-ish tint like this cheapo shi-et oil.
70ml came out of it.

Sticker claimed 80ml of oil, possible as at least 10ml will get stuck inside and we can't remove it.




I filled up 24ml of genuine Denso ND-8 which is so clear so nice so clean. WIS called for 20ml. I added 4ml as buffer.
Denso guide is a bit more oil than MB WIS for this scenario.





I am surprised that ML/GLE400 using 1,050 grams R134a vs our typical W212 using 590 grams R134a, is using the same total oil capacity of 120ml for single evap code 580 ????
So it is correct that EVAP has the highest oil keeping capability on the HVAC, see the Code 582 uses 40ml more oil due to 2nd EVAP and extra longer hoses.



Our typical W212, also 120 ml



---------------- 590 grams vs 1,050 grams---------------





-----------------------


Pressure test for 30 minutes or so with nitrogen, no leak. Good.
Vacuum for 5 hours, down to honest 500ish microns.
Fill r134A to 1,042 grams.

And start the engine ...............


.



.




Holy crap, I can't even turned off the HVAC, compressor goes to full power. Cold yes, but the A/C-REST button is still blinking, blower is still strong, HVAC controller no response to any of my key input

So I choose this menu :






.





IT WORKS !!!!!
Now the HVAC computer N22/7 is back to its normal control-able by me...operation....yipee.

Now the question is, what made N22/7 to be in that DORMANT-BUT-COMPRESSOR 100% - AT ALL TIME state and no DTC telling us/me to do compressor breaking-in.
I know the compressor is new, but what set of events does it take to make N22/7 defaulted in this "EVIL DORMANT" state ?
AA.Maybe , few times valve controller deemed short circuit and low pressure on R134a as read by the sensor ?
BB. Maybe, having AA issue and car is still in use, cover some mileage ???
CC. Other unknown-s.....

It is stupid state this EVIL DORMANT-state , it keep trying to power up 100% the compressor control valve (1) . It keep powering up interior blower at 60-80% speed (2)....WTF ???
Why dont it just blink like Christmas tree and do not do the two harmful things above ?

Does our W212 N22/7 have similar stupid EVIL DORMANT strategy ?

----------

Back to fake Denso compressor.
This fake compressor is under-sized.I do not know its true mechanical identity, so this is all I could tell u guys.
At idle it will do 100% , that is not how our W212 behave.

Almost 4 minutes into the compressor running, it is still 100% power applied to the compressor. At this point I am still using FRESH AIR, hot outside air.


.

I have to raise RPM to 1,200 RPM or more like below 1,500 RPM to lighten the compressor Control Valve load , as faster spinnning engine and compressor = more displacement or more work done.


At 9 minutes AC running, I already chose RECYCLED air, thus evap temperature hit 2.4C.


See, if I use only idling speed, EVAP can't hit even 3-4C, let alone 2 Celsius. See 8.3C below.



So the con of them M-Fkr counterfeiter is to sell you under-sized compressor....which I am certain mechanical wise is not as good as Denso in terms of operational longevity.
Just so you guys know, MB Indonesia wanted US$1,900 for the MB genuine Denso compressor for this car.
This car , Denso catalog does not even list the compressor for it.... Dugghh !!!!
Some MB cars, you can't get compressor from Denso. Luckily my W212.065 , I can get from Denso...nice
Maybe originally this ML400 uses Sanden ? I don't know man.

Anyway, I am happy all turned out well and I got a new know-how on the N22/7 un-documented strategy or SOP, whatever you wanna call it.
I also got to test an original Denso control valve, read here : https://mbworld.org/forums/e-class-w...-how-test.html

I hope this the fake Denso to last at least 3 years.


-------------------

Final stress test this morning....




At high enough RPM, it can go even lower. Cold start morning, so engine bay is cool and I was doing 1,200 - 1,400 RPM before this photo.




What wil happen in Jakarta crazy crawling daytime traffic jam which means 600 RPM most of the time.....with this fake Denso ?
Its evap temperature will be 7-8C at best and vent output will be 10-11C, approx. Decent but not good and compressor 100% loaded all the time.


END.

 

man you're also expert in HVAC :O amazing. 2015 car year ac compressor already gone bad? I hope mine will last :O . It seems replacing or fixing hvac systems in mercedes needs some serious skills

 

I have zero HVAC experience (that and rebuilding transmissions are the only automotive tasks I've not yet mastered). This doesn't make me want to dip my toes in, but fascinating all the same. Glad I live in a cool dry place!

 

This compressor is the 3rd one from brand new car.
Supposedly the new owner got it like 2 weeks ago only, a used car.

MB Indonesia I think has poor QC for HVAC evacuation/vacuum and R134a charging.
My car was short of like 150+ grams of R134A in 2023.

Toyota Thailand , my wive year 2020 Corolla Cross had good HVAC works. I done RRR on it in 2023 too.

 

Yep, cool place say 20C , is already a big smile from me, perhaps 60% humidty only max....I will be smiling all day.