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Thread: Weird HVAC issue

  1. #1
    Join Date
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    Weird HVAC issue

    I have a feeling it is soldering related... When put in the "manual" mode (face, feet defrost) I will have heat for about 15 minutes then it goes full cold, it will do it on either side. I have tried without the heater valves plugged in and it made no difference at all. When switched back to auto mode and it goes to the foot well vents I get full heat back. If I have the temperature setting on anything other than full it will operate at that temp from 5-10 minutes then go full cold also and heat will come back when switched back to the full temp position. The air coming out the driver side will be half the force of the passenger, it is not a broken actuator for multiple reasons, it has randomly started working correctly and will completely shut off when on auto with heat.
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

  2. #2
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    are slow
    IHKA control panel

  3. #3
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    11/88 E32 750iL+98 E36M3
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
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    I have resoldered the control panel a few times, I can try my spare one in the car and see if that makes a difference.

  5. #5
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    In case it is not the control panel, maybe if you have a spare IHKA control module, change that for a test. Also needs resoldering . Here a collection of possibilities/repairs I made http://www.bimmerboard.com/forums/posts/419686/
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
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    Finally got around to investigating this further, I took the IHKA from behind the box and found a few interesting things. The blue capacitor on the left near the top of the board on mine is blown and im not sure of the spec to order. The positive temperature coefficient (round blue piece in the middle of the board) is blown and I dont know the spec. Finally for the last one the mosfet at the left on the top left heat sink is blown too and once again spec is not known. Would anyone possibly know the spec of these pieces? I would try and look myself but I only have one of these and its way too cold to run without one.
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

  7. #7
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    Last edited by shogun; 02-15-2018 at 03:52 AM.
    Shogun tricks and tips for the E32 series are HERE!

  8. #8
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    I continue to exhibit similar problems as yours, even though I have replaced the IHKA control module and fan limit switch (blower sword) from Programa. I'm wondering now if it is me not knowing how to operate the control panel, a fault in the control panel (i've tried two different ones now, one was blowing fuses for my seats, the other does not, and neither correctly controls the air in the car), a faulty rebuilt component, or something more sinister in the electronics department. I know the flaps work, because i've had different temperatures come out of every vent.

  9. #9
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    This shows you the parts needed, that is a modification with cooled version of the IHKA control panel, 3 MB http://www.e32-schrauber.de/bmw/date...difikation.pdf
    The IHKA control unit repeatedly failed after about one hour of driving. In “cold condition” (directly after starting) the unit worked perfectly. The possible root cause was overheating of the entire unit. The housing is completely closed and on the PCB there are several components generating considerable heat. As a solution an active cooling was built in. The cut-outs are located over the components which generated the largest amount of heat. The two fans (30x30x7) were built into the “step”
    of the housing; there is enough space to the opposing electronic components.

    At the upper end of the PCB both +12V (KL 15) and ground can be found. There are two massive tracks adjacent to each other. Here a connector was soldered on (after removal of the protection coating, of course. Grind it until you see shiny copper…).

    There are 5 diodes (1N4001 or eqiv.) between +12V and the fans. The fans are running more silently at 10V (13.8V – 5 x 0.7V).
    For testing this modification the temperatures at two components (heat sink left – Temp 1, resistor right – Temp 2) were measured. Until about 4400 sec. (1 ¼ h) the control unit was idling – just supplied with 13.8V,no switching, no stepper driving, nothing – but 65°C at the resistor! Then the fans were switched on…
    During messing around with the IHKA control unit to determine the cause of the malfunction I tried to find out more about how the IHKA was built up. Unfortunately the main components (microcontroller, driver IC’s,…) are marked with a special code – sorry, no proven information about these items.Thus: all following information is based on my own fuzzy thoughts about how this unit may work…(Picture and overview at the end of this document)
    The IHKA control unit is diagnosis capable, i.e. (almost) all of the currents / voltages are measured and supervised. This is done by the power resistors together with the LM2901’s which compare analog values (set/actual) and deliver a corresponding digital signal to the main controller. This may evolve to a real PITA as each signal which is not exactly inside the defined limits will trigger an error message. If some values drift over the years there may be error messages where no errors are…

    The stepper motor’s four windings are switched low side (ground) by the ULN2003’s. The bit pattern is stored by the stepper controller into the shift registers (HEF4094) which pass the signals on to the ULN2003’s. There are two driver-IC’s for switching the heating valves etc. (unfortunately these IC’s are coded: L475D). And exactly here is one of the big puzzles of the circuit: adjacent to these drivers there are two 120 Ohm power resistors. But those are not in a ground path due to current measurement or similar, they are just powered – a heating! Why? No clue… I only know one reason for providing such a “senseless” load: even in idle mode the control unit draws a defined amount of current and may be detected by other components of the entire car system.
    But: exactly those resistors generate a considerable amount of heat! All pictures I found in the web show a nicely tanned area on the PCB around these resistors… thus I milled the openings in the housing directly above them.

    The next heater is the PTC of the fan of the interior temperature sensor. A PTC acts like a fuse. In normal operation it has a low resistance and passes current through. If there is too much current (e.g. a short), it gets hot and changes to a high resistance. The problem: if it gets heated from the “outside” (the overheated housing) it will change to a high resistance and the main controller gets the error message: “short in the fan”. This may be the main problem of the IHKA control unit…

    Last not least there is the main switch transistor. It is located on the same heat sink as the 5V voltage regulator for the digital circuitry. The transistor switches the KL30 supply (always hot) onto the internal KL15 (hot on ignition). Thus the control unit is powered during the often cited two minutes after engine stop and is switched off after this time. Again a problem: the main transistor itself is switched by secondary switching transistors. Latter ones are the said BC337’s. If they burn out the main transistor is permanently powered and it will never shut down the control unit – the battery will be empty soon enough (…it needs to power the fancy 120 Ohm heating…).
    The main controller is very likely one of the Motorola MC6805 family. Some of the pins can be determined with a high probability (supply, Xtal,...). The reset pin was very interesting – the trace leads to one of the LM2901. In the original condition this part of the PCB was very sensitive, as the circuit remained in reset state if I touched one of the inputs of the LM2901 with the scope probe (!). After having changed the “surrounding” capacitors, this phenomenon has disappeared…

    If the IHKA control unit is already opened and the soldering iron is ready I would change the two BC337 and the capacitors which are populated nearby the heat sink (2 x electrolytic caps, 2 x tantal caps).

    last page large pic of all components:
    ? (coded) wahrscheinlich Optokoppler,possibly opto couplers (X610: 18, 19, 20)
    ? (coded) Treiberstufen für Heizungsventile, Zus.-WaPu, Frontsch.-Heizung ,(siehe Kommentar!) driver stages for heating valves,aux water pump, windsh.-heating (see comment!) (X610: 21, 22, 23, 24)
    ? (coded) Schrittmotor-Controller stepper controller
    ? (coded) Haupt-Controller main controller Motorola MC6805 (?)
    2 x CD4051 Analog-Multiplexer für verschiedene Sensorsignale for different sensor signals
    PTC Innenfühler Lüftermotörchen (Kommentar!) small fan for inside temp-sensor (see comment!)
    ? coded – but for sure: 5V-Spannungsregler 5V voltage regulator
    ? unreadable: Haupt-Schalt-Transistor main switch transistor
    2 x BC337 (NPN) Hilfs-Schalt-Transistor (siehe Kommentar!) aux. switch transistor (see comment!)
    Schutz-Dioden protection diodes
    4 x BDX53 (NPN) Treiber Schr.-Mot. Frischluftklappe stepper-driver fresh air flap
    6 x ULN2003 Schrittmotor-Treiber stepper-drivers (low side)
    5 x HEF4094 (8-bit shifter) speichern Bitmuster für Schrittmotor-Treiber store bit pattern for stepper-drivers
    „DA-Wandler“ / „DA-converter“ PWM > Kondensator >Spannung für „Gebläse-Schwert“ PWM > capacitor > voltage for „fan-sword“
    7 Widerstände / resistors Stromüberwachung Schrittmotoren current stepper drives
    3 Transistoren BC547 (NPN) für MPX-Taster for MPX switches
    CA3240 (Op-Amp) Verstärker für „Schwert-Spannung“ amplifier for „sword voltage“
    5 x LM2901 (Comparators) Spannungskomparatoren voltage comparators
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
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    Jun 2017
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    I was tooling around behind the radio and decided to feel the driver side mix door actuator and found the little plastic bit that connects the actuator to the lever broke off. I manually closed the door and now there's full airflow both sides. I ordered an eBay motor with that plastic piece still on there, is there any easy way to get viewable access to get that lever on the motor without removing the dash? My thought is behind the instrument cluster but it's hard to tell.

  11. #11
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    You have to try, when we did that we removed the side carpet at center console on each side, each panel 2 screw.
    Removed IHKA control panel
    Removed the radio
    Center grill on dash to see the flaps moving
    and one of the wood panels besides the radio
    But that is a EURO model, no airbags, no knee bolster protection.

    It makes it easier if you also remove the covers under the steering wheel, Basically study the pics from Johan about dashboard removal, then you see what you need
    http://bmwe32.masscom.net/johan/dash...al_v1.1-1.html
    of course, not all the steps are necessary.
    There are also good pics on a German site, he repaired the broken stepper motors
    http://www.e32-schrauber.de/bmw/
    click in index Innenraum>>Heizung, Klima>>.Klimaanlage, then scroll down.

    Or you remove the center console too, then it looks like this http://www.bimmerboard.com/forums/posts/1044927/
    more info
    http://www.bimmerboard.com/forums/posts/884367/
    dashboard removal in 20 minutes, by Johan, I posted that here http://www.bimmerboard.com/forums/posts/779402/
    Shogun tricks and tips for the E32 series are HERE!

  12. #12
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    Just a thought - It is winter and you want heat, so you could just leave the vent closed and disconnect the stepper motor.

    Only you will know that you did this.

    Sometimes Manual Override is best.
    Last edited by E32FAN; 02-24-2018 at 08:18 PM.

  13. #13
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    The funny part is, it will still change temperatures just only at the maxes and will take a bit for the heat to fully dissipate. I did just get my new actuator in yesterday so hopefully it wont be too difficult to get the lever back on the actuator.
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

  14. #14
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    I managed to reinstall the new motor and lever through the radio hole and it definitely takes some very bendable fingers to do so. Full blower and temp control are back. However, my auxiliary heater pump is not being turned on and is not getting 12V at the connector. Thoughts anyone?
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

  15. #15
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    The coolant must have a certain temperature before the aux water pump starts. The aux pump has a capacity of 950 l/h and kicks only in when heater is on and from a certain minimum coolant temperature (I think it is 36 degree C) is reached.
    Engine heating comes first.
    Check that function first.
    Shogun tricks and tips for the E32 series are HERE!

  16. #16
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    When I tested the connector the engine was near full temp still so apx 75 degrees C. I did find somewhere that the exception to that is if the heater controls are set to full heat that it will turn on the aux pump regardless.
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

  17. #17
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    Copy that German language file under heating Airconditioning> Klimaautomatik IHKA (German language PDF) http://www.e38.org/e32/
    section 5.8 page 36 is control of aux heater valve , also a function diagram.
    The running is also dependent on the setting of the temp control left and right.
    If you need a transmation, retype the text and use google translate.
    But first unplug the connector to the pump and test directly with 12V, maybe the pump is gone. Usually the plastic at the bottom of the pump breaks and inside is the motor for the pump and then the coolant destroys the pump motor.
    Shogun tricks and tips for the E32 series are HERE!

  18. #18
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    After I got the pin out to the relay I did some testing, 12V at the socket and 12V that's supposed to go to the pump. Bypassed the relay to test and got 12V at the pump connector swapped in a spare yellow relay I had and bingo the pump switched on for the first time. I still need to order a new black relay so that my windshield defroster works along with the pump. How does my U.S. spec car have the defroster windshield? I always thought that was a European only thing.
    To summarize:
    Weird temp control/mismatched airflow was due to drive side actuator failing resulting in residual heat with AC providing the feeling like it works then doesn't.
    Missing 12V from the aux pump was due to a failed relay.
    Last edited by yukon101; 03-24-2018 at 12:54 PM.
    New Daily:
    2011 Audi A6 Avant 3.0T prestige. 1 of 368

    ----FOR SALE-----
    04 BMW 325xi 143k


    The Fun car:
    94' BMW 740i 308k miles

    Fresh 72k mile engine with all new seals. True E34 Manual Trans Engine Harness. 6spd Transmission Swap, Getrag 420G. RHD LW Single Mass Flywheel. E39 M5 Clutch. E39 M5 Shifter. Factory Car Phone. Factory 6CD Changer. Factory Electric Sunshade. Not So Factory Factory Electric/Heated Rear Seats. E38 Heater Valves. E43 M5 calipers/brakes

    Sold:
    1996 Oldsmobile Aurora; 194k miles but with a bad paint job and dented fender resulting in a payout to buy the 740i

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