Resetting the climate control AC computer - Mercedes-Benz Forum
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#1 (permalink) Old 03-06-2011, 10:26 PM
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Resetting the climate control AC computer

Hi guys,

I have had my share of problems with my AC unit. Recently though I am unable to get it to blow cool air. Yesterday for a moment the AC was blowing cold air through the center vents and HOT air through the side vents. Today I can't get it to blow cool air through any vent even if I reduce the temp to the coldest setting "LO".

If I keep the AC temp at 72 and auto, the air through the center vent is warm but the side vents are warmer, outside temp is in the 60s and the cabin gets warmer and warmer. Last month the AC computer went erratic and my fan speed was jumping up and down automatically even if I kept it at 1, 2, 3 or 4, then my temp reading went from F to C and back to F!!!!

I always use the EC setting for winter. For summer I manually keep temp between 60-70. I never set it to auto and leave it all year round as some do. Today, neither auto or manual temp control seems to work.

There are no lights that stays on to indicate a problem as some have referred to (EC light), my compressor seems to come on more frequently these past couple of days. I know I may need some freon, duo-valve cleaning, evap, maybe new compressor, etc. This all is for the spring.

Till then, does anyone know how to reset my climate control system using the climate control buttons available on the front panel? I have read that you hold down a couple of buttons for 10 secs, then restart the car, then I have also read other stuff. I have read that there is a diagnosis mode but I have never been able to activate that following those instructions.

Anyone know of the reset sequence to my AC system? Would you know how to initiate the diagnosis routine as well?

Thanks.
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#2 (permalink) Old 03-07-2011, 05:34 PM
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First of all I don't think your compressor is bad. I don't know of any sequence to properly to do a diagnostic on that type of control unit without STAR. (Perhaps someone will chime in and enlighten me)
The problem most likely is the the fading control unit itself, not uncommon. There may be cold solder joints within the unit itself among failed resistors, capacitors, etc. It can be repaired.
I would invest in a maniflold guage set for the a/c so you can check low and high side pressures to aid you in further diagnostics. B
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#3 (permalink) Old 03-08-2011, 12:40 AM
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Thanks B.

In my searches I found the following doc, and pg. 102-110 have AC related diagnostics and their codes. I'll have to check this out tomorrow. But I am doubtful this will work. I tried similar sequences before. If not, STAR it will have to be.

Maybe you can guys can try and see if these sequences yield anything on your cars.
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#4 (permalink) Old 03-08-2011, 07:04 AM
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have you checked your blower regulator?!?

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#5 (permalink) Old 03-08-2011, 09:31 AM
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How would you check that? My blower seems to work fine. The air coming out is not the right temp.

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#6 (permalink) Old 03-07-2014, 12:31 AM
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Hi
I got the error code 69, says auxiliary fan stage 2 problem,
I recently rebuilt AC compressor and whole system by changing o-rings and seals, oil and recharged with r134 and no leak in system. I cleaned heater dual valve (one seemed stuck) and now that's fine.
I already know I have a vaccuum problem for vents, but while turning AC on, no cold air come from side vents, well it is different from heater, but not like you feel the coldness of AC.
Tested climate control unit and the only code was 69, tried to delete it but it remains on. I know aux fans take huge part in cooling, but even in the cold morning when I turn on the AC, still not satisfying.
Any idea?
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#7 (permalink) Old 03-07-2014, 07:56 AM
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The condensor has to have air drawn across it in order to work efficiently. If your auxillary fans arent working, your gonna have to fix that first. That may not be all of your problem, but it is probably a big reason as to why your ac is not cold. This is assuming that you have a full charge and are circulating freon. If you arent moving any freon, its not going to get cold either. You can check this by putting your hand on high and low side ac lines. One will be much colder than the other. If you have this, you are circulating freon.
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#8 (permalink) Old 03-08-2014, 01:32 PM
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Thanks for you reply George.
I talked to mechanic who repaired compressor, He said as your system were out of fereon for long period, it will take some time for regulators on compressor to pass all gas.
Anyway I have an error 69, for aux fan stage 2, it has nothing to do with gas pressure as far as I know, that's all about temp switch. I have a big black relay for aux fans instead of two separate one with fuses, relay seems ok, but I still have this code, and I believe my aux fan wont start if engine temp reaches 105 C. I don't know where the problem is?
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#9 (permalink) Old 03-08-2014, 03:15 PM
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I'm not sure I understand your mechanics reply. If it was out of freon, he should have drawn a vacuum on the system for a minimum of 30 minutes to an hour to pull out the air as well as any moisture that may be in the system. Then add an ounce or two of pag oil and charge. The ac is a sealed system. It will not purge any air out of any kind. If it does, then you have a leak that needs to be fixed.


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#10 (permalink) Old 03-09-2014, 11:25 PM
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I had a leak on compressor, I completely fixed it, drew air and moisture from it, then charged it with fereon. But when I bought the car 1 month ago, it was out of gas? for how long? We're not sure. but now leaks are fixed.
main headache is that we scanned the car for reading codes and in KLA section it says: Auxiliary fan not operating, check relay K9 or fuse. We can read some codes through climate control unit too, and I exactly get same fault, code 69--->aux fan stage 2 problem.
http://www.benzworld.org/forums/w202...stage-2-a.html
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