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Thread: Help Me Fix My AC Woes

  1. #1
    Join Date
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    Help Me Fix My AC Woes

    My AC has been blowing hot air mixed with the cold air...during the summer it becomes pointless to run the AC. There is no problem during the winter getting heat. I have diagnosed my AC with DIS and got the following see pics below. So after taking things apart to see as well as with the diagnoses, I am concluding that maybe my AC control unit might be bad...does this conclusion makes sense? The unit #64118391512 is no longer available, and I would need to visit the junkyard. I say the control unit because the diagnoses points to the white plug pin 10/12 and the blue plug pin 13/14. I also provide the electrical diagram of the Integrated Climate Regulation.












  2. #2
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    Hi my friend,
    I'd like to ask you to humor me just a minute. I really don't know what the "SG" plug is....but I know a couple of things that cause your symptoms....and one of them points to pin 21 on the x16154 connector: maybe that's the SG?

    See that brown dust in the little tiny round grill, in your picture? Before doing anything else, blow that grille out with compressed air. If the unit can't read the interior temperature, it can't give you the temp you've asked for.

    THEn, I'd suggest using electrical contact cleaner, and spraying both sides of every plug into the control unit.

    The system is old, and stuff gets dirty. Let's try the FREE fixes first. If this fails, yes, you likely need a new module / control panel, but try easy first.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
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    Quote Originally Posted by bmwdirtracer View Post
    Hi my friend,
    I'd like to ask you to humor me just a minute. I really don't know what the "SG" plug is....but I know a couple of things that cause your symptoms....and one of them points to pin 21 on the x16154 connector: maybe that's the SG?

    See that brown dust in the little tiny round grill, in your picture? Before doing anything else, blow that grille out with compressed air. If the unit can't read the interior temperature, it can't give you the temp you've asked for.

    THEn, I'd suggest using electrical contact cleaner, and spraying both sides of every plug into the control unit.

    The system is old, and stuff gets dirty. Let's try the FREE fixes first. If this fails, yes, you likely need a new module / control panel, but try easy first.
    Hey Chris,

    That "SG" had baffled me until yesterday when an M3 forum member said SG = in German Steuer Geraet = control panel or control device. I had also thought of getting a can of electrical cleaner as mine was complete empty but you're right for me to try that first. I'll also vacuum out that dust too.
    Last edited by NolliM3; 09-26-2018 at 10:20 PM.

  4. #4
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    There's a forum member locally who brings his E46 to me. His a/c blew hot and cold, and I fixed it by blowing out that temp sensor vent.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  5. #5
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    Quote Originally Posted by bmwdirtracer View Post
    There's a forum member locally who brings his E46 to me. His a/c blew hot and cold, and I fixed it by blowing out that temp sensor vent.
    Chris, I did clear that sensor and I were surprised to see the gunk that was in there including dog's hair...didn't resolve the AC issue...so will get the control device next.

  6. #6
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    Have you cleaned both sides of all plugs in the back of that control unit with electrical contact cleaner? After all, you have 4 pins which are being called into question. Maybe they've got some green deposits around them, causing a bad connection.

    Most "computer" issues I see are corrosion issues. In one way or another, that old "manual" IHKR seems to have connectivity issues. since blowing out the vent didn't help.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  7. #7
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    Quote Originally Posted by bmwdirtracer View Post
    Have you cleaned both sides of all plugs in the back of that control unit with electrical contact cleaner? After all, you have 4 pins which are being called into question. Maybe they've got some green deposits around them, causing a bad connection.

    Most "computer" issues I see are corrosion issues. In one way or another, that old "manual" IHKR seems to have connectivity issues. since blowing out the vent didn't help.
    I'll definitely try that first (forgot)...I'll be out-of-town for a few days and when I am back, Ill do that...thanks for reminding me!

  8. #8
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    Quote Originally Posted by bmwdirtracer View Post
    There's a forum member locally who brings his E46 to me. His a/c blew hot and cold, and I fixed it by blowing out that temp sensor vent.
    And so far, so good. With my issue, it would usually blow cold initially, and might even continue doing so for a 20-30 minute commute, but when it failed it would just start blowing hot air at a high fan speed (when on auto setting; I could still change the fan speed manually, but it would still blow hot air). If the car was turned off and back on, it would continue blowing hot regardless of temperature setting, but often after sitting until the engine cooled significantly, it would initially blow cold again. Chris saved me from throwing parts at it (I replaced the FSR/FSU, which is kind of a pain, a few years ago for a erratic fan speed issue. I was considering a heater control valve before Chris figured it out. I thought maybe it was sticking even though that did not make a lot of sense). Good luck!

    edit: additionally, the "hot wind" phenomenon also occurred when the compressor was not on (when I was running the vent with ambient air). So, if anyone stumbles into this and has a similar or identical problem, you might just need to blow out the temp sensor vent!
    Last edited by mry82; 10-01-2018 at 10:48 PM. Reason: additional clarification
    H&R Sport Springs, Bilstein B8s, and poly bushings (Thanks Chris!); Valeo SMF & non-SA Clutch, CDV delete, and E60 Shifter w/ ZHP knob; Beisan System VANOS Seals...
    Mtech-II Front Bumper (PO got bumped in parking lot!); Eagle Eye LED Tail Lights... Lots of PM!!!

  9. #9
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    The evaporator has a temperature sensor (thermistor) that tells the IHKA the temperature of the evaporator. If the evap’s temperature gets too low the IHKA will open the heater control valve to send hot coolant into the heater core. The air flow, btw, is up through the heater core and then through the evaporator. This prevents the evaporator from freezing up. I’d check that sensor as it may have “gone off the rails.”

  10. #10
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    Hey Chris,

    I am back and wanted to spray some electrical cleaner; however, I could not figure how to easily remove the connector to the IHKR control module and I don't want to rambo and break anything...see pic below. Also, I forgot to share that I have noticed that sometimes when I go on a drive and shut off the car, I get a gargling sound from the heater core as if something were boiling...MarcoZandrini's post reminded me to share that info. Since what the IHKR seems to not getting a 5v info, could that imply the temperature sensor as MarcoZandrini suggested? I had noticed that gargling sound when I changed the heater regulator to a new one hoping that would have resolved my problem.


  11. #11
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    Let's use the blue plug, as an example:
    The white part of that plug is a pivot. It needs to rotate from left to right, following the curvature of the plug. To rotate it, you'll need to push down a little elevated piece, right in the center top of the plug, which is locking the pivoting piece in place. No force required.

    Personally, I doubt if the heater core is the source of your gurgling. As these cars get older, they pretty much all make funny noises after you shut the car off, from flaps, motors, and the like.

    Having just re-read the thread, I'd suggest that you see whether the heater control valves (under the hood) are getting power on the yellow wire.

    When these valves do not get power, they are in the OPEN position, meaning that they are feeding hot water into the heater core. Similarly, if the valve unit fails, hot water will be in the heater core.

    IS FUSE 31 GOOD ? Hot both sides?

    I'm going to try to attach a fairly long BMW Tech magazine article on the HVAC system, for you. It may take two posts to attach it, because it's a large file.

    - - - Updated - - -

    Pages 3 and 4. Sorry that they're sideways, upside down, etc...
    Attached Images Attached Images

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  12. #12
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    I would follow exactly as DIS has instructed. The Steuergerät is the control unit (or Gerät can translate to device as well, but in this case control unit is a better translation). Check the voltage to make sure the SG has ~5V at the specified plugs/pins to rule it out. The pins should be numbered once you get the connector apart.

    Also a good idea to clean out the interior temp sensor first as suggested.

  13. #13
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    Quote Originally Posted by bmwdirtracer View Post
    Let's use the blue plug, as an example:
    The white part of that plug is a pivot. It needs to rotate from left to right, following the curvature of the plug. To rotate it, you'll need to push down a little elevated piece, right in the center top of the plug, which is locking the pivoting piece in place. No force required.

    Personally, I doubt if the heater core is the source of your gurgling. As these cars get older, they pretty much all make funny noises after you shut the car off, from flaps, motors, and the like.

    Having just re-read the thread, I'd suggest that you see whether the heater control valves (under the hood) are getting power on the yellow wire.

    When these valves do not get power, they are in the OPEN position, meaning that they are feeding hot water into the heater core. Similarly, if the valve unit fails, hot water will be in the heater core.

    IS FUSE 31 GOOD ? Hot both sides?

    I'm going to try to attach a fairly long BMW Tech magazine article on the HVAC system, for you. It may take two posts to attach it, because it's a large file.

    - - - Updated - - -

    Pages 3 and 4. Sorry that they're sideways, upside down, etc...
    Hello Chris,

    When I downloaded the images, it's very small making it unreadable. I will send a PM with my email address so you can attach there.

    I checked fuse 31...it was good; however, I could not remove the plug from the water control valve...my hand when in a fist shape as I grab onto the plug to squeeze the tab pressed against the intake manifold fins...hurts like hell. The jiggling of the plug seems to stop the gurgling or I haven't heard it since...I watch and listen to it. In the mean time, I wanted to ask whether it's possible for the water control valve to some how trap coolant...every couple of days I need to top off the coolant reservoir, about a cup, (it yet there is no leak or coolant on the ground.


  14. #14
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    I didn't design the location and plug of the Heater control valve.

    Are you filling the expansion tank above the full level? If there's no room for expansion, the cap will vent pressure and coolant. Otherwise, either you have an external leak, or you have an internal leak....like the head gasket. The coolant is going SOMEWHERE.

    You might want to check the little tubes which collect condensation from the a/c evaporator. These are underneath the car, above the transmission. If these are dripping COOLANT, you need a heater core.

    Otherwise , take the car to a BMW shop and have them do a pressure test of the cooling system.

    Really, you're going to need to check that plug for power, whether it hurts or not. I bleed, pretty much every day, working on cars.

    I've emailed you that document.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

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