Polar Bear

Hi all,

I have a very clean E320 4-Matic M112 Sedan, and recently I have been getting a commonly reported issue with many Mercs, in which the cooling/A/C fan runs full speed when the ignition is turned on. No malfunction is reported in the MFD until engine start, and then the fan runs full speed. From my research, all 4-matics have a single fan, and mine seems to have the 380W Bosch fan. I recently replaced the AAC panel due to LCD liquid leaking, and I felt this could have attributed to it as it was a different part number. I replaced it with the original part number, the same one listed in EPC, and coded it to use K2 CAN connection to the IC; The IC is coded correctly to an M112 4Matic, 80L tank, etc. I have never been able to get this MFD error and full-speed fan issue to go away since it began. DAS shows the coolant temp in normal range as does the AAC unit.. The Quick Test in DAS always results in an ME SFI 2.8 Fault, with a P1999 code -open circuit to radiator/A/C fan. The AC works fine, and I have noticed no other issues. I have checked all codings I could find referencing an Auxiliary Fan to Not Present in the AAC, and some other modules, but this was not an option for the EIS. Another very odd symptom is when you you enter Actuations and Radiator and A/C Fan Tests in the ME SFI 2.8 Control Module, it allows you to actuate the speed from 10% to 90% for testing. This actually works in reverse, and when set on 10% the fan is at full speed, and when raised to 90% it is nearly still.

I have not encountered anything similar, so any assistance would certainly be appreciated!

Thanks!

Plutoe

post your VIN!

Polar Bear

Polar Bear

Plutoe

Assuming your ECU, coolant temp sensor, fan control module, cluster and AC control unit are not faulty the fan on\off ratio is 10-90% where 10=off, 20=on min speed and 90=on max speed---if the fan runs at high speed there is a fault-------the one area you did not comment on was making sure the IC was and or is coded with "automatic air conditioning", you need DAS or the HHT for that simple procedure.

Polar Bear

Polar Bear

Polar Bear

Another interesting side note, is that the actuation performed by the ME 2.8 from 10% to 90% always operate in reverse - 10% is highest speed and 90% is almost nothing. This is also confirmed when both AUTO buttons are pressed on the AAC module, and when I removed the fuse for the fan to allow the vehicle to idle and charge the battery, monitoring the temperature. It reached 212F so I replaced the 50 amp fuse, and the fan did not come on, so I am sure the ME was requesting the fan to function at high speed, it was at this time the fan was doing nothing. After shutting it down and starting it back, the fan came back on, with the warning message, and cooled the engine quickly.

Polar Bear

I wanted to follow up on my original post for people that run across this in the future.

A little backstory - I have owned two W210s and they were both E55 AMGs, and the were both nearly new - a 1999 and 2001. This was one of the cars that really got me into the brand (and an old W123 300D Turbo Diesel I paid $1200USD for and was so impressed by the engineering and simplicity).

I sold the 2001 E55 AMG around 2007, and have owned a W211 E320 CDI, an S600 S-Class biturbo (which I still own) and still navigate back to the W210. Love the body style, build quality, and technology that was very advanced for the year. So as a daily driver, I found this 2001 E320 4Matic 210.082. It was very clean, had almost all options I was looking for, less than 200k, one owner, very well maintained, and very clean with no accidents. It has heated seats, COMAND, leather in wonderful condition, and a great running strong engine. I have so little invested in this car, I wanted to improve the things I could reasonable improve, such as replace the Automatic Air Condition pushbutton control with the leaking LCD chemical turning parts of the display black and causing segments not to work. I also knew how to repair the few pixels that were not working on the cluster, but was able to get both of these in perfect condition for next to nothing. I installed the cluster properly, zeroing out the odometer which allowed DAS to identify it as new, so I performed an Initial Startup and Transfer Settings from Previous Unit. The transferred the mileage over (which was most importantly done to ensure legality, and also the replacement had less mileage, so the next service or state inspection would reflect a lower mileage and taint the vehicles history forever on CarFax, etc. All of the ASSYST history was transferred over as well, so I had a digital record of oil changes, replinishments, etc.

As I was improving the condition of this car and enjoying it very much while doing so, I wasn't aware of the differences in the AAC pushbutton controls logic and how they varied, and I was introduced for the first time of the difference in the engine and A/C condenser fans on different W210s and how they operated. A 2002 E430 4-Matic, for example, has three fans, and my car has one fan behind the radiator - an electric fan that cools the engine and serves to cool the A/C condenser. Speaking with folk about how to code the replacement AAC to my car (either using HHT or the pushbutton control itself) I was consistently told the car had an Auxiliary fan and it needed to be set to "Present" although the it was not clear in WIS or other sources if this was correct or incorrect. To me, Auxiliary Fan implies that it is supplementing another fan, for example, a "Primary Fan." If only one fan is present, it is supplementing nothing and is the sole fan for all cooling operations on the car. To shorten the story, following what I had read and input from others, I set the AAC control unit to believe an Aux Fan was present, and every other control unit that had that setting. I honestly don't remember everything I "checked as I was getting to know the car. I had more knowledge of the W221 S-Class and W211 E-Class as I wasn't into diagnosing the W210s when I had them (not to mention neither of the E55s were in the shop one single time!).

I have also read that many control units play a part in controlling this electric fan speed - the ME SFI 2.8, Instrument Cluster, AAC Pushbutton module, various temp and pressure sensors in the car and for the R134 refrigerant, and the K76 unit that takes a PWM signal from the SAM and controls the volume of air and speed the fan operates at. So any one of these modules could potentially be bad, so I had to start looking at the ones I replaced first as the car did not do it when I first acquired it.

To make this long story short, another post regarding a W203 had the same issue, and the solution was the EZS had not been coded correctly when it was replaced at another time. I attempted to check the EZS/EIS coding for this setting on mine, but it was not exposed in HHT, so I was thinking perhaps after initial configuration, this may could not be changed or altered.

Drawing at straws and testing wiring and other reinstalling prior control units and not fixing the problem, I thought I would try an old diagnostic machine I still had to see if it exposed any additional settings compared to the version I was working with. Sure enough, HHT exposed Variant Coding - an option that was not there in HHT for the EZS in the newer version. I went into this menu and it was corectly set to W210, but Aux Fan was set to present. Already determining (and having nothing to lose) this setting just might go against what I had been told and needed to be set to Not Present, I coded the EZS and wrote it to the control unit. I turned the key to "Run" without starting the engine (where previously the fan started instantly even without the engine running) and heard nothing. I started the car, and the IC immediately displayed the trip and main odometers (previously within one second of engine start, ENGINE FAN VISIT WORKSHOP would be displayed).

The problem was immediately fixed and everything has been perfect since.

I have little doubt in my quest for learning these vehicles and knowing more about them, how they work, etc., that I inadvertently changed this setting in the EIS, but I *am* confused as to how since that setting was not exposed. A Quick Test comes up completely clean except for the backup antenna for the Digital Tele-Aid. A/C cools excellent and car is doing great!

For people that find this post later, I reverted to 10/2008 DAS to locate the setting that was missing all along.

Thank you to all of the people that helped!