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Thread: E46 Auto Climate Control Continually Blowing HOT Air.

  1. #1
    Join Date
    Apr 2015
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    2002 325xiT 5-spd

    Question E46 Auto Climate Control Continually Blowing HOT Air.

    Hi All,

    My new (to me) 2002 325xiT's climate control system is a lot more complex than my old '89 e30's was. I have the Auto climate control system, and it is constantly blowing hot air. I've searched around and have seen others with a similar issue, but I can't find a clear resolution.

    Symptoms:
    -Hot air(really hot) will blow from the foot and windshield defogger registers. The fan speed will vary if I adjust the desired temp, however these remain hot even with the A/C on at the coldest setting.
    -The center of the dash blend valve when set to the coldest will allow the cool outside air in, however will blow the same extremely hot air if turned to the neutral position, or anywhere in the red zone. This seems to behave somewhat normally.
    -The air that blows hot is extremely hot, not just a symptom of a poor A/C charge.
    -Manual fan speed controls work, but there is no way to direct cool air from both the windshield or foot registers.
    -The complex system with numerous fans and servos to control air getting sent between alternating sets of vents seem to work okay as the defog will blast air up top, and I can direct air to the feet normally.

    Possible issues:
    -Water flow valve to heater core? I've seen posts that this could be stuck, and many where they have been replaced with no change.
    -IHKA issue? Could this be an annoying issue that I'll have to take to a mechanic that has the original programming equipment to somehow "reset" the system?

    Any thoughts, ideas, or suggestions for a repair would be greatly appreciated as summer is quickly approaching!

  2. #2
    Join Date
    Sep 2006
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    Can you turn off "auto" and get cool air out of the feet and windshield vents?
    Quote Originally Posted by B4SH View Post
    If anyone knows, it's this guy who knows literally nothing about everything.
    Quote Originally Posted by fcvapor05 View Post
    Do you even OT? The mean 401k around here is probably about $6, what with all the shiny cars and $1,000 watches and donations to get other members' Volvos running.


  3. #3
    Join Date
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    I've tried turning off the Auto function. After the car is warmed up, even turning down the temp all the way and turning up the fan, it is still blowing hot air from the windshield or foot vents. I can control which it goes to, but can't get them cold. When I focus the air through the center of the dash vents, they will (generally) to to the temp indicated by the position of the center mix valve. They won't however blow anything colder than the ambient outside temperature.

    Having the AC on and the temp set on Auto to as cold as possible, with the mix valve on three blue dots seems to be the only way to keep the cabin mildly comfortable. It is currently spring, so temps during the day are a pleasant 18.5c/65f or so. I'm just getting worried about the summer that is approaching!

    I'm thinking that the system must be able to sense the cabin temperature, as when it is set to the coldest temp, it will not try to force hot air through the system. I don't think that this can be accurately sensing anything, or is not relaying proper commands through the IHKA, as even set to a cool (not coldest) temp, it will start to blow some warm air.

    I know that the internal temp sensors are below the center dash vents, and I've been sure that they aren't blowing cool air directly down (giving a false temp reading that would tell the IHKA to push hot air).

    Thoughts? Ghost in the machine? It seems that this must be more of an annoying electronic issue than something with the mechanical systems that direct the air.

  4. #4
    Join Date
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    2018 BMW M240i
    My first suspect would be the coolant valve or power to it. It sits on the intake side of the engine on the inner fender. Remove the air cleaner box to access it. Remove the connector and with the engine on check for 12VDC when you've set the climate control to ac. This valve is designed to be open unless it's receiving voltage. Why? Some BMWs reside in very warm climates. The owners never use heat. The coolant residing in the heater core gets old and the core fails. This design allows fresh coolant to circulate through the heater core when the engine is shut off.

  5. #5
    Join Date
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    '15 I01Rex , '11F25
    Quote Originally Posted by MarcoZandrini View Post
    My first suspect would be the coolant valve or power to it. It sits on the intake side of the engine on the inner fender. Remove the air cleaner box to access it. Remove the connector and with the engine on check for 12VDC when you've set the climate control to ac. This valve is designed to be open unless it's receiving voltage. Why? Some BMWs reside in very warm climates. The owners never use heat. The coolant residing in the heater core gets old and the core fails. This design allows fresh coolant to circulate through the heater core when the engine is shut off.
    I learn something new everyday, I thought power closed was a fail-safe so if the valve lost power you would still have defrost.

  6. #6
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    Quote Originally Posted by awscheuf View Post
    1) I've tried turning off the Auto function. After the car is warmed up, even turning down the temp all the way and turning up the fan, 2) it is still blowing hot air from the windshield or foot vents. I can control which it goes to, but can't get them cold. When I focus the air through the center of the dash vents, they will (generally) to to the temp indicated by the position of the center mix valve. 3) They won't however blow anything colder than the ambient outside temperature.

    Having the AC on and the temp set on Auto to as cold as possible, with the mix valve on three blue dots seems to be the only way to keep the cabin mildly comfortable. It is currently spring, so temps during the day are a pleasant 18.5c/65f or so. I'm just getting worried about the summer that is approaching!

    I'm thinking that the system must be able to sense the cabin temperature, as when it is set to the coldest temp, it will not try to force hot air through the system. I don't think that this can be accurately sensing anything, or is not relaying proper commands through the IHKA, as even set to a cool (not coldest) temp, it will start to blow some warm air.

    4) I know that the internal temp sensors are below the center dash vents, and I've been sure that they aren't blowing cool air directly down (giving a false temp reading that would tell the IHKA to push hot air).

    Thoughts? Ghost in the machine? It seems that this must be more of an annoying electronic issue than something with the mechanical systems that direct the air.
    1) So you've "tried", but does the "auto" turn off?
    2) what's the temperature outside?
    3) That's what the center vents are designed to do. When set to all blue dots and the A/C isn't turned on, you're getting outside air into the cabin.
    4) This is true in general, but specifically, the temp sensor is behind the little 1" square grille in the IHKA unit.
    Quote Originally Posted by B4SH View Post
    If anyone knows, it's this guy who knows literally nothing about everything.
    Quote Originally Posted by fcvapor05 View Post
    Do you even OT? The mean 401k around here is probably about $6, what with all the shiny cars and $1,000 watches and donations to get other members' Volvos running.


  7. #7
    Join Date
    May 2014
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    Renton Highlands, WA
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    e36, e46, e90
    I actually have the exact same problem as OP from what it sounds like. Specifically any time I turn on the heat on any form (whether auto climate or manually) it blows the same temperature air out of the vents (really hot air). The only part that makes it super annoying for me is that I have to turn the air off to cool down and then back on 5min later to keep the windows from fogging.
    Last edited by Das Omen; 05-04-2015 at 05:20 PM.
    Du bist die kraft, die macht und die prophezeiung in Ewigkeit, du bist das Omen.

  8. #8
    Join Date
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    Try this BMW-approved process:
    - disconnect the ground/earth/negative cable from the battery
    - repeat for the positive cable at the battery
    - short the 2 cables together for at least 10 minutes
    - reconnect the positive cable to the battery
    - repeat for the ground/earth/negative cable
    - reset the clock

    This process forces all computers to reboot. I've seen it cute several electronic issues.

  9. #9
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    Try removing your air box and reach down besides the left front strut tower, there will be a cylindrical solenoid that should be very hot, disconnect the electrical connector of your heater valve and check for voltage by either using a grounded test lamp or a DVOM, if with key on and IHKA set to a low temp and the lamp lights, replace the heater valve, while you have the valve removed, if you have access to a garden hose, try to collect as much of the old coolant as possible and back flush your heater core with fresh water.

  10. #10
    Join Date
    May 2017
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    2004 325xi Touring
    ptarditi - Bringing up an old one here, I'm dealing with this same issue. Funnily enough it start after I got the car back from an engine swap. All the same symptoms as above and I have tested it and am getting 12v to the valve, but I played around with different IHKA settings and seem to get 12v all the time. Shouldn't that change depending on settings? Anything else I can double check before ordering a new valve? Thanks

    Quote Originally Posted by ptarditi View Post
    Try removing your air box and reach down besides the left front strut tower, there will be a cylindrical solenoid that should be very hot, disconnect the electrical connector of your heater valve and check for voltage by either using a grounded test lamp or a DVOM, if with key on and IHKA set to a low temp and the lamp lights, replace the heater valve, while you have the valve removed, if you have access to a garden hose, try to collect as much of the old coolant as possible and back flush your heater core with fresh water.

  11. #11
    Join Date
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    Newburyport ma
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    88,m5 95 740 04 XI E90
    Yes remove the valve and see if its all corroded inside or just stuck open. Common problem. Heater control panels fail too.

  12. #12
    Join Date
    Jun 2015
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    Raleigh, NC
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    '98 M Roadster
    I had this issue and it was fixed by replacing the "heater control valve." $80 part when I bought it a few years ago, and a DIY install. There are videos on YouTube.

    Sent from my Nexus 7 using Tapatalk

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