A/C control unit 20 pin info / schematics

Discussion in 'Engine' started by KLee, Feb 9, 2006.

  1. KLee

    KLee Hardcore MB Enthusiast

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    Hi all, I finally dismantled the centre dash to get at the a/c control unit behind the fan speed and direction dials. The part number was found on the top of the black unit, mine read 210 830 0185. There is a barcode sticker on the bottom with Edmontage PL printed on it. Have checked wth MB and they recognise the part and new part is whooping AUD$965 = GBP402 !!! :eek: (only 1 in Singapore and lots in Germany)

    I asked my mech to see if he can diagnose the circuit board to repair the existing one... he doesn't have the circuit diagram (or equiv) cos my unit has 20 pins whereas the units here in oz have 25 pins.

    Can anyone help with pin information / readouts/ schematics please - what other info from me would one need? I searched on Edmontage but no results. How can I find out who made this control unit or is it definitely MB? I'm really desperate now. (In prev post my radiator was leaking and guess what - it f split!! A *new* one GBP270 is being put in!! (on a 10 yr old car :mad: ) and now I'm guessing its needs to be wired up to the control unit too hence all these issues ... I'm dead in the water unless I get a some info on the pins or fork out another GBP402!! :mad: The joys of MB :crazy:
     
  2. miro

    miro Hardcore MB Enthusiast

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    If you pre-pay an order with me I will supply that same unit for half the price.

    Who told you that the control unit is faulty ?
     
  3. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Hi Miro
    Thanks for replying and your help. Regarding whether control unit is faulty ... long story in my post below - problem started end of Jan. Summary - initially sent to a/c mech who tested and concluded its the control unit. I probed but he did not say if he had a diagnostic tester that concluded this. I then took car to my regular mech who also does electronics (who is now doing the radiator) and I believe needs to hook up radiator sensors to the control unit.

    Aircon not kicking in immediately

    And this post #15 of mine starts discussions when an a/c specialist looked into it and concluded it was the control unit (but I didn't quite trust his work...just a feeling so I pulled the car back)

    Any chance you can or know handyman chaps around who can test/repair the circuit board? ;)

    For my sanity, is your prepaid one the exact same unit and does it need adapting/programming or straight swap (that even I can do?) Importantly Do you also have wiring diagrams info so my mech can complete his radiator install? I found this but my guess is this is the newer 25 pin one, not my 20 pin one - where can I find the 20 pin schematic? Help

    Really appreciate your help.
     
    Last edited: Feb 10, 2006
  4. miro

    miro Hardcore MB Enthusiast

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    The solution to your problem is to prevent yourself from becoming an air-conditioner specialist. All of these people with "experience" are giving you a birds eye view of the problem. I would prefer if the TX switch was checked and make sure you have sensor and valve operation.

    I really feel that you are asking the wrong question. The question you should be asking is ....

    why does someone with no idea of my control unit pinout think that it is faulty ?

    Without some proper diagnostic at a Benz dealer I wouldnt even think of starting this problem solving. Because you are already going around in circles and ordering parts randomly.
     
  5. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Miro, I'm with you and I agree. I couldn't have had hoped more than anything it was one of the other things that were faulty - the mechs have assured me they checked all those a/c component out. But that is why I pulled the car from the first mech - to get a second opinion.

    In the meantime, the radiator blew. So the current mech isn't looking into the same a/c problem (yet). He is tasked first with installing a new radiator and part of that requires hooking up to the control unit (if I am wrong on this sorry, pls tell me and I shall give the mech a bollocking!).

    When he gets to looking into the a/c not working and his opinion is not good enough I will send it to MB for diagnosis. (I was only preparing looking around for the a/c control unit in case that was indeed the faulty part)

    Priority is looking for and appreciate any help regarding getting my mech to complete the radiator install (does it really need hooking to the a/c control unit)?
     
  6. miro

    miro Hardcore MB Enthusiast

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    With a radiator and AC that old .... jumping the gun and going for a module swap is premature.

    Which tests have been done ?
     
  7. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Ok previous a/c mech relayed that no power was being supplied to the a/c compressor so he supplied test power to it and said the a/c system worked and cooled the cabin. Can we infer from this the a/c components like refrigerant pressure, pressure switch, drier (replaced last year), tx valve (replaced last year) are good and working. Fan works at all speeds. Heater works too. I havnet cleaned the cabin temperature sensor in the dome light.

    Checking the a/c circuit diagram on Autolib Russian site, to understand why and if a/c control unit and radiator have anything to do with each other, I see connections to the ECT sensor and the Coolant Circulation Pump. These may not be the components but if they were, to me, it seems obvious to re-connect the components to their own wires as before and let the 20 pin connector map it to the a/c control unit. I don't understand why this would prompt my mech to ask about the a/c control unit at this stage.

    Actually given my radiator went south could the ECT sensor be affected and impact the a/c control unit?
     
  8. miro

    miro Hardcore MB Enthusiast

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    Does the control module have a fuse ?
     
  9. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    I don't know. Anyone? I do know the EC button still lights up accordingly and the others rear demister and air recirculate lights up and works fine. Since these are fronts to the whole a/c control unit more likely means the fuse is ok. The car is at the mechs so can't check relay box. I will chk the manual. ... yep as I suspected there is a fuse #12 10A (red) for Automatic heater/climate control. This has been checked by mech.
     
    Last edited: Feb 11, 2006
  10. miro

    miro Hardcore MB Enthusiast

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    Did all of the pins on the wiring harness check out ?
     
  11. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Spoke to mech for an update this Sat morning. Then just saw your question above and havent asked the mech. But just to confirm do you mean the 20 pins on the socket wired into the car (not the one on the control unit) testing each pin with multimeter for voltage? I will ask.

    I have cleared up the radiator issue - he has completed the radiator install :)) ) and wasn't asking about the a/c in relation to that. He was ahead of schedule so was already looking into the a/c issue. Following todays update from him basically due to differnet number of pins he cannot carry out any solid diagnostic scans - not on the control unit nor on pressure switch. He has confirmed if the compressor is supplied with power the a/c works and cold air blows into the cabin - so the issue is only that one cannot activate the system via the EC push button. Based on this for complete diagnosis I'm leaning towards taking it to MB after I confirm with them what they intend doing as part of the a/c diagnostic.

    Unless ... given 2 mech have confirmed the a/c system operational with the only issue being inability to activate it via EC button, I look at the odds and it seems a good bet replacing the a/c control unit will fix the problem. Miro though I might already know the answer to this it can't hurt to ask, can I 'try' out your new control unit? If it doesn't improve my situation, any chance we can work something out?

    I'd be so :devil: if it was something simple like a dry or cracked solder on the PCB board ... the day the a/c went kaput it was a very HOT day high 30's deg celcius and the car was already parked overnight outside so it got about 3 hours of high heat whilst stationary before I drove off.
     
  12. miro

    miro Hardcore MB Enthusiast

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    What if a wire is broken .... thats not even in the control unit.

    I dont stock these parts you will need to order it at your own expense.
     
  13. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Update ... I probed and according to the mechanic, the a/c control unit only checks 1 component before supplying power to the compressor. That component according to him is the pressure switch. Because mine has 4 pins whereas his scanner only accepts 3 (the ones used here in oz), he can't scan it to conclude 100% if the reason the a/c control unit is not supplying power to the compressor is due to the pressure switch.

    I found a pic of my pressure switch from a bunch of engine bay photos - I can just about make out the 4 pin connector. Can anyone please help with wiring diagrams for the 4 pins? Can anyone also collaborate with the finding that only the pressure switch is checked as part of supplying power to the compressor? Thks
     

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  14. jasohal

    jasohal Hardcore MB Enthusiast

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    If it helps, on my '95 model w124, the control unit supplies 'ground' via a pressure switch to the KLIMA relay which in turn powers the compressor.

    If the relay is ok and system has enough gas (pressure) then the control unit should supply the 'ground' signal for the A/C to switch on.

    If you can get to the wires on the control unit you should be able to probe for a ground signal when the car is started and when either the EC button is pressed or dehumidify id pressed.
     
  15. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Jasohal, every information bit helps! Thanks heaps, I will relay that on ... you make it sound so simple to test and operate. When you say supplies 'ground' via a pressure switch, do you mean THE pressure switch on the drier? Can you also tell me whereabouts is this relay? I read somewhere about this KLIMA ... wonder what mine is.

    I have since learnt my pressure switch is SSP043118 made by Diavia.
     
    Last edited: Feb 13, 2006
  16. jasohal

    jasohal Hardcore MB Enthusiast

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    On my car the A/C relay ( also called KLIMA ) is behind a plastic guard which itself is behind the battery located against the bulkhead on the passenger side when viewing from the front.

    If the control unit is supplying ground but there could be a problem with a pressure switch ( on my car there are two , one low and one high ) as one is situated in line from the control unit to the A/C relay it will stop the compressor from engaging

    On my car, the pressure switch is only two pin and I can by pass it by just 'jumping' both connections this will rule out the pressure switch.
    ( Providing your A/C relay is ok ).
     
    Last edited: Feb 13, 2006
  17. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Finally AC all sorted. Just update for benefit of all, thanks to all who replied. I passed on all info I gathered to mech. My AC system is installed by Diavia not MB but some parts were MB. Main issue was lack of information regarding the Diavia system, installation and wiring. I managed to get in contact with Delphi Diavia in UK, technical manager Andy Craddock is the superb chap that kept a dialogue going with me helping me relay critical info, gave me wiring schematics and prompt my mech with suggestions and hints. If anyone wants the full wiring diagram for the Diavia AC system for 1996 C220 or C280 let me know.

    Key info was that for Diavia installations, the MB AC control unit and its wiring does not control any of the AC functions - they only used the EC button to close the loop. Instead it is the 4 seperate wires which are not part of the wiring harness can be seen coming out of the control unit going into engine bay to a relay on passenger side just beyond windshield under the bonnet. Two of the biggest delays in diagnosis is that (1) the relay mentioned was actually missing in my engine, according to the mech. I believe the orig AC specialist who looked into this ( that I didnt trust and pulled the car from to send to the current one) removed it and didn't replace it - you can imagine my anger at this. (2) The Diavia installers has reused the fuse slot for Dome lighting in the fuse box and didnt relabel it! How dissapointing.

    In the end it was the 1 relay and 1 fuse that was the problem. My mech opened the control unit and PCB, testing everything, followed all the wiring, drew his own circuit diagrams to find the faults. All fuses inline were replaced for futureproofing. Main cost was labour in diagnosis. Thanks again to all.
     
  18. Shude

    Shude MB Club Veteran

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    Excellent news! :D
    This is very poor, was it documented anywhere in the diagrams or instructions?
     
  19. OP
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    KLee

    KLee Hardcore MB Enthusiast

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    Nope. Just looked at the wiring diagram, I can see fuses but no indication of where it is located. I guess info missing are illustrations of locations of the various components. In all my excitement I havent yet asked the mech details about exactly which fuse # it is and where is the actual dome lighting fuse then etc - he has it all drawn up for future ref.
     
  20. miro

    miro Hardcore MB Enthusiast

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    Also an affirmation that a control module seldom fails when it is doing very little hard work indeed. The clue to me seemed to be that it was performing other functions unrelated to the problem but wouldnt interface with the problem directly.

    Nice to see that the problem was one of operational switching logic and not expensive hardware. Good stuff !
     

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