Finally I got it done and it works now with fine cold air to the rear.

 

Great news!

 

Can someone please give me a link to the right Ind chip.
The link above what is given rather points to a few of these Ind chip's.
i have te same problem .Myn 2004 E200 is blowing very hot air from the rear vents when the AC is on. I Replaced the heater control valve under the wiper motor and still have the same issue.

 

Okay, so I have the same problem. Replaced heater control valve twice and no effect. One mechanic said it has to be the blend motors, and I bought them, but getting to them is insane. And I have my doubts that it is the blend doors, simply because even when the thing is blowing cold, I can feel heat around the rear vents, as if there is hot water circulating back there.

I also have the intermittent symptom, where it is correctable by rolling either the front or rear thermostat up to HI and then back down, then it's good for 5 to 10 to 20 minutes, but if it's hot outside, then we go right back to very hot air coming out the back.

So before I rip the car apart to replace the blend door motors, I think dealing with the SAM is a good idea.

Used SAMs are widely-available on Ebay, but I think they have to be reprogrammed at the dealer, and why do that when you can just replace the chip and reinsert the existing SAM without having to program anything? There are a zillion wires and connectors going into the SAM, so getting it out is something that has to be done carefully, but otherwise that is plainly the move.

The SAM is an expensive part, even at Husker Parts (www.mbdirectparts.com). But the chip is available from Digikey for $2 each plus $5 to $7 shippping. It's one chip, in 3 different packaging formats. Get the packaging format that allows you to buy a single chip rather than 1000 of them. I bought 3, because at $2.37 each, I don't want to pay to ship it again if I manage to screw up the chip. I can always resell the others on ebay.

https://www.digikey.com/product-deta...61-1-ND/677588

That's the chip.

Here's the video:
I'm going to have my Indy pull it and take the thing to my local computer repair shop, where they do a lot of soldering circuit boards, to replace the chip.

I will let you know how it goes.

 

Good post. I'm going to call that company tomorrow and see how fast I can get a few chips to Seattle. I like your idea of getting a few.

 

When I ordered online from that page I linked, I think it was like $7-something to send 3 of them to NY by Priority Mail, and a buck more to send it FedEx Ground. But Priority Mail is uber-reliable 2-days to my place, so that's what I did. They have a wide assortment of shipping options; this is a place that obviously serves big-volume corporate customers, as you will see from the online order form. But they make it equally easy for a guy like me to order a single-chip, and they give you literally 10 different shipping options. Seems like a good vendor.

 

I just placed my order.

 

UPDATE: I ordered three chips in case I messed one up. I took apart the the front SAM which was no problem. I have never removed a chip from a board. I bought a desoldering pump and a brand new iron. It took me 30 minutes to get the old chip free from the board. It was not at all easy.

After the chip was out, I tried using the existing solder. I was able to get the chip where it looked at least decently positioned, but the solder connections were iffy. I put it back together and had cold air for 20 minutes. It got hot again.

My buddy Dima at Dudmd came through big time. He had the chip off the board in about 10 seconds using a hot air station. Also had the chip soldered back on in about the same amount of time. I couldn't even tell it had been touched. The car has about 45 minutes drive time with cold air at the rear.

So long story short is that you need the proper soldering tools and know how for this to work efficiently. Again, huge thanks to Dima at Dudmd in Auburn, WA. He is the guy to go to for any ECU needs.

 

They make solder wicks too. Soaks up liquid solder with copper fiber. Might be cheaper for one time use.

 

So the three chips I bought were sitting in my car most of the summer, because I couldn't coordinate with the guy that was going to do the chip replacement. Had I known for sure that this would fix it after FOUR YEARS of screwing with it and almost -- at one idiot mechanic's advice -- pulling the whole HVAC unit out (removing the dash, etc.) to replace an allegedly non-functioning flap motor before I found this thread, I would have worked harder to get the chip replaced.

SO, here's what happened. I finally decided that I would buy a SAM on Ebay and swap it in, then drop my SAM off at my guy's place and let him do the soldering at his leisure. Even if the new SAM worked, I would want to use mine, because I know everything else on it was good.

I paid $50 for an equivalent SAM (long story I should tell some time) on Ebay. I was super-careful about labelling each wire with its place number on the old SAM. Turned out I really didn't need to, as there are colored dots for each of the similar connectors, and most connectors aren't similar. But the exercise really taught me where everything went, so it was productive. Most of the connectors were easy; some were a bit of a challenge, but I eventually got them all undone. Put in the replacement SAM and went to program it. Ignition key wouldn't turn. Looked up which fuse did the ignition key. Replaced it. Key worked. Recoded the couple of codes that needed to be changed on the replacement SAM, and I was in business. These old SAMs don't require SCN coding; the new ones do (which are just remanufactured old ones). One caution for anyone going this route (and I should write up a piece on it if I have time): just because the model of the SAM is identical to yours, don't presume that you can just drop it in without programming. If you have a normal 211 like I do, and your SAM came off an AMG, you've got a problem. The relay in Position R on all but AMGs is the Secondary Air Injection Pump relay. On the AMGs, that relay is placed elsewhere, and the relay in Position R is for the Oil Cooling device (which we don't have). One of the codes that you tell the SAM is essentially whether position R is Oil Cooler or Air Injection Pump relay. That's the major difference, but there are a few others.

Interestingly, my replacement SAM had all the error codes stored in it for stuff we now know are common problems: Secondary Air Pump relay, and, of course, the dreaded Heater Changeover Valve. I cleared them, but figured that I wouldn't freak if this didn't work, because the old car's defective Changeover valve might have fried the relevant chip on this SAM, too.

But, long story short, it did work. Magnificently. It was clearly the chip that was the problem. It has now been two weeks of hot weather, and I still find myself reaching back to see if there is cold air coming out the rear, and there always is!!!! I'm gonna put the new chip in my old SAM, and keep it as a backup.

There's a guy on Ebay who is replacing the power connector on my Kindle Paperwhite (another constant problem with an electrical device); he does it the same day for $19.99, return shipping included. Hundreds of positive reviews; the guy is very busy resoldering stuff on Amazon products. I'm gonna see if he is interested in doing this kind of chip replacement, and if so, I will post the info here in case folks can't find somebody local.

This is an amazing, amazing fix to a problem that has stumped myriad mechanics, including those who work all the time on W211s. They all know about the changeover valve, and they know that the dealer always wants to replace the SAM for anything mysterious, but they aren't going to recommend that route in case it doesn't fix the problem.

SO, here's my advice: if you have replaced the changeover and it doesn't fix the problem, and you have hot in the rear that can be temporarily "tricked" by rolling the rear temp up and down and the problem then returns 5-20 minutes later, you would do well to try this fix. Find someone familiar with electronics who will be around for a couple of hours while you get your SAM out of the bonnet, and bring him your SAM with the instructions here and the $2.17 chip that you got from Digikey pursuant to the instructions above. Most likely, you will be very glad you did, and, if you're like me, you will wish you did it much sooner!!

 

UPDATE to UPDATE:

So just a follow-up. As I mentioned earlier, I had found an identical-model-number used SAM on Ebay, which I installed as a stopgap while I dropped my original SAM off at my buddy's. We never could coordinate our schedules so that I could remove my SAM, take it to him, have him fix it, and take it right back to the car. So I put in a $50 used one and dropped mine off for him to fix at his convenience. The $50 one worked so well that I didn't pressure him to do the work, because I wasn't really sure I wanted to risk damaging a wire bundle or connector by doing repeated surgery in the SAM box.

Big mistake.

The $50 SAM worked flawlessly for two weeks. Then I started to get some weird behavior in the car. Cluster resetting once a day when I stopped at a light after the first 10-15 minutes of driving. Then twice. Then 3 times. Then, all of a sudden, pretty-often. Then when I put on the lights or wipers. Etc. Some things like the radio were unaffected. Clearly, some power-related thing in the car was dying a slow death. Battery? Voltage regulator? A diode somewhere? (This mimicked the slow death of a power diode in a computer I had a few years ago, so I had a sense of what it was. But where?) So I changed the battery, which fixed everything for a few days. Then it came back with a vengence. The charging system and battery all checked out on the voltmeter. No helpful messages on DAS, just some newly-stored messages that certain things weren't communicating, but nothing current.

Fast-forward: After it went completely-haywire, I went to my Indy. He thought maybe an intermittent ground by the BCM, and we cleaned that up and voila! Fixed! Nope. A few starts later, back to the same old. Clearly, disconnecting power for 15-20 minutes relieved the problem (like it did on my old computer), but only temporarily. Finally, the starter wouldn't turn over, even though there was power in the circuitry.

Long story short: it was my $50 SAM. When I realized that everything that was going bad ran through the driver-side SAM, I asked my buddy to please please please change the chip on my otherwise-perfect original one, because my car was now not driveable. He did the work that night. I put it in 2 days ago and all problems cleared up. Plainly, something started dying in the used SAM for some reason, and it just got worse and worse.

My buddy's chip-replacement was meticulously-done, and the a/c in the rear now works flawlessly when controlled by my original SAM. So the lesson learned is that it is much, much safer to just find someone competent to change the relevant chip in your original SAM than it is to brave the used market, even if the parts are reasonably-priced. My $50 one came off of a wrecked car, and I guess it stands to reason that it could have been exposed to the elements enough to start it down a path to a slow, painful death once it was put back into service. Or something...

But, hey, even with all the agita, I now have my air conditioning working perfectly for the first time in years, for the price of a $2.37 chip and a little donation to my buddy. Given the price of a new SAM (and the fact that the new version (which is all they now sell) has to be SCN coded, which my dealer will only do if you buy it from them and they install it), I wouldn't have been inclined to throw all that money on an untested theory that the problem with the rear A/C blowing hot air was caused by a defective chip in the SAM.

And, for what it's worth, my buddy used a hot air station, carefully-protecting the surrounding things on the board with special tape, because he said they can get messed up and you wouldn't even know it. Then, after replacing the chip, he got out a microscopic viewer he uses to make sure that there were no bridges in the new chip connections and the surrounding area of the board. He found and corrected a few. So it seems that this is not a DIY job unless you are really used to working with electronics.

 

This is a revival of this great thread. I am one of the less lucky ones who recently bought an '03 E320 for my daughter and among the issues I am fixing is a non-functioning heater control valve M16/32. I replaced M16/32 valve, but unit still does not function correctly in Star functional test. I discovered this last nite after replacing the valve. The valve was certainly bad. Coolant had leaked into the motor and gummed it up so that it wouldn't turn even after I removed from housing. A little PBlaster and some freeing up of the armature and it was running like normal (I presume). Draws only about 200mA at 13V no load, but draws upwards of 1A when held still (winding resistance load).

A little internet research led me to the Youtube video from the Belgian shown the L9997ND motor driver IC on the Front SAM PCB.

I've ordered some of the ST Micro N9997ND chips which appear to be the one one board in the original video.

I also found some good info on hand solder replacement of IC's.


Ordered the Fast Chip special solder shown in the video along with some solder wick, etc.

This is going to be an interesting deep board-level repair.

I can't bring myself to buy the ~$350 MB rebuilt Front SAM without giving the board-level fix a try.

Should be able to get it done next week.

Will post results.

 

Okay. You got the right chip if you ordered what I mentioned in my post 2 years ago.

My buddy (who did this professionally for years) used an air station, and said it was still tricky to make sure he hadn't shorted something else out on the board. But lo and behold, he did a great job and the repair worked perfectly then and works perfectly now as we are going once again into the air conditioning season here in NYC.

I have no doubt that the valve (a PITA to replace) was in fact fried. That's what burns out the chip. Valve seizes, chip burns out in many cases as a result.

You're doing the right thing to try this. If you have someone who does it for a living, you'll probably be glad you let them do it.

 

I've hand soldered some SMT components before. That part that keeping me up last nite was the removal of the bad chip, This is the tough part as too much stress on the leads will pull the pads off the FR4 board matl.

I got up and did some searching and found that trick with the Indium solder. Fantastic! I'm surprised I never learned about that from an earlier job where we had some board builders. We even used Indium for some other applications. They had special de-soldering equipment for specific chips etc.

The pitch on leads of the SO-20 package is 0.050in. It's small, but do-able. Nowadays they go significantly smaller which makes replacement a lot tougher without special tools.

This whole architecture of CAN bus control of driver devices to operate motors is not very fault tolerant for the inevitable usual motor failure mode of excess mech resistance causing motor load to slowly degrade to the winding resistance and the CAN bus is doesn't know anything about it on the logic input side. The chip datasheet says it has 'overcurrent protection', but this doesn't protect it from repeated 'hammering' with the logic side giving signal to 'turn it on' again and again.

The only software design fix I can think of that they could do is to disable the function from the logic side on the CAN bus once the system receives 'implausible data' in correlating temp change with CAN bus instructions to M16/32 valve motor. I guess they thought that would be too severe or prone to false negatives in inferred diagnosis.

The change from the W140 (which I still have) to this W211 for my daughter is a major deep dive into the tech angle with both DAS and stuff like this control architecture.

Last nite was discouraging after the valve replacement, but now I'm on a new mission albeit with some degree of trepidation.

 

Amazing the info available on this board...

 

I went to visit my MB mechanic master/teacher and told him about the matter of not getting warm air after the M16/32 heater valve replacement and that I thought I was going to have to fix the Front SAM.

He promptly dismissed this notion immediately and said that the front SAM hardly ever goes bad. He said that I was going to have to re-calibrate/initialize the motor thru DAS. I told him I had already done the test for M16/32 in DAS and that this was not yielding the desired change in temp at the vents.

He said to go back into DAS and poke around and there is a place to re-initialize the motors of the climate control and that there is also a place to force the motor open and closed and to see actual values of movement; kind of like with the Hall effect sensors, but that it doesn't have a Hall effect sensor.

Armed with this new info, I went back at it last nite. I hadn't put the wiper system and all that stuff back as I wasn't sure it was fixed. I poked around in the Auto A/C control unit and found routing to re-initialize the motors and also a routing to check the function of the motors. I ran both of those and then seemed to be getting warm air out of the vents with the A/C off. This was encouraging. I then ran the M16/32 function test, which was not so clear as you are supposed to have A/C on full cold, then operate the heater valve and look for temp change at effluent air on the vents. With A/C on full cold, the temp delta between the 2 states is only spec'd at about 10° F (I think). Without temp sensor it's not so easy to discern Pass/Fail.

I did note error for Front SAM (Driver's SAM) for M16/32 and also disconnected wiper motor. I cleared the errors and then went back into Auto A/C control unit and had my wife Open & Close M16/32 while I felt the heater valve motor for indications of operation. The motor worked in positions.

What is also interesting about the M16/32 Heater Valve motor operation is that the valve basically just opens & closes; it doesn't operate continuously. The drive signal runs the motor for 1~2 sec and it throws it Open of Closed. In operation, it is working kind of like a narrow band O2 sensor, bouncing Open/Closed, but with a much longer time constant driven by temp changes in the cabin or climate control as detected by sensors. This shows why blowing the motor driver chip on the Front SAM is a rare thing as it is only seeing the 1A max current load in spurts as it tries to operate the heater valve.

Well , there's another chapter in the W211 repair. Now on to replacement of 2 fixed vent windows in rear doors and replace A50 radio with modern Android radio/Nav/Bluetooth unit.

Lucky to have the help of the master once again.

 

Hi, my w212 has the same problem. Went to the dealer and they changed the valve flap for $200 (include labor). Was happy enjoying the cold air for 3 days, but then it went kaput again. I'm quite frustrated by now. I live in Jakarta, Indonesia, and its quite an embarassing sight when u have to open the panoramic and all the windows when driving a merc, whilst being drenched in sweat.

The mechanic said then it must be the climatronic modul which will cost an eye-watering $800 (include labor).

Question is, can i do the chip replacement fix on my w212 too?

Thanks!

 

Ok I just wanted to say THANK YOU to moehler for posting the info on this. I just did it to my E500 after replacing the duo valve and it not working. The L9997ND was the issue and thanks to having soldering experience I was able to replace it. I did an entire live stream of the repair and test in the car if anyone wants to watch it for a DIY guide. Thank you again

Video of the repair and installation: https://www.youtube.com/watch?v=lyfh...ature=youtu.be

 

Very impressive. This was a lot of work for me when I did it, between carefully removing and reinstalling the SAM and having my friend with the air station carefully doing the soldering, but here we are with 202,000 miles on the car and everything still working great. A $1200+ SAM replacement at the dealer was avoided for the price of a cheap, readily-available chip. Thanks again to all the knowledgeable folks on this board!

 

@moehler

I see you're in NJ too. Are you able to DM me where you had this work done? I'm experiencing the same issue and have the L999 chip handy. I just don't trust myself to do the work. I'm in the Hunterdon County area.