C5 climate control flap issue.
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Thread: C5 climate control flap issue.

  1. #1
    1000+ Posts George 1/8th's Avatar
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    Default C5 climate control flap issue.

    Hi Froggies,
    I recently posted a quick fix to the climate control flap issue. Yesterday I noticed the passenger side was still cool, but just a little warmer than the drivers side. I figured my quick fix was a little too quick and needed revision. So, I came up with a simple and revised modification which could be easily reversed if necessary.
    I also took photos. C5  climate  control flap issue.-16-shaft-socket-flap-motor.jpgC5  climate  control flap issue.-17-shaft-part-servo.jpgC5  climate  control flap issue.-18-new-shaft-part-progress.jpgC5  climate  control flap issue.-19-testing-new-shaft-part.jpgC5  climate  control flap issue.-20-snug-fit.jpgC5  climate  control flap issue.-21-testing-shaft-end.jpgC5  climate  control flap issue.-22-how-looked.jpgC5  climate  control flap issue.-23-position.jpgC5  climate  control flap issue.-24-motor-back-place.jpg

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    I just used some flat beading because it weighs nothing, is easily cut and shaped. The photos should tell the story, the screws that hold the servo motor in place are 6mm. You just need a 6mm small socket. To access this you simply remove your glovebox, about 10 screws. If we call my modified shaft part " the stick", the final thing I did to fit the stick was shorten it till it's overall length was about 16mm. I just used a stanley knife to shape the stick. It just has to be wide enough to fit into the flap spline without pressure, so it's not expanding the shaft, and it has to be a firm fit into the inner recess of the servo motor spindle.
    While you are at it make two "sticks' the same and fit one to the upper Servo as well. These two motors and flaps work together to control the climate control, so both must be working mechanically together as dictated by the computer.
    I changed to using beading to get about 3.5mm thickness. cheers.
    Last edited by George 1/8th; 4th February 2015 at 10:49 AM.
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  2. #2
    1000+ Posts George 1/8th's Avatar
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    Quote Originally Posted by George 1/8th View Post
    Hi Froggies,
    I recently posted a quick fix to the climate control flap issue. Yesterday I noticed the passenger side was still cool, but just a little warmer than the drivers side. I figured my quick fix was a little too quick and needed revision. So, I came up with a simple and revised modification which could be easily reversed if necessary.
    I also took photos. Click image for larger version. 

Name:	16 - The Shaft socket on Flap motor.jpg 
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Name:	17 - Shaft part of servo.jpg 
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Name:	18 - New shaft part in progress.jpg 
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Name:	19 - Testing new shaft part.jpg 
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Name:	20 - Snug fit.jpg 
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Name:	21 - Testing shaft end.jpg 
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Name:	22 - How it looked.jpg 
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Name:	23 - In position.jpg 
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    I just used some flat beading because it weighs nothing, is easily cut and shaped. The photos should tell the story, the screws that hold the servo motor in place are 6mm. You just need a 6mm small socket. To access this you simply remove your glovebox, about 10 screws. If we call my modified shaft part " the stick", the final thing I did to fit the stick was shorten it till it's overall length was about 16mm. I just used a stanley knife to shape the stick. It just has to be wide enough to fit into the flap spline without pressure, so it's not expanding the shaft, and it has to be a firm fit into the inner recess of the servo motor spindle.
    While you are at it make two "sticks' the same and fit one to the upper Servo as well. These two motors and flaps work together to control the climate control, so both must be working mechanically together as dictated by the computer.
    I changed to using beading to get about 3.5mm thickness. cheers.
    One further modification/ update. I think this should be the final fix for this little problem.
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  3. #3
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    Default Fixed !

    Hi George1/8th
    Thanks for your detailed fix with photos. That should help some people into the future

    A couple of comments to add from my experience for reference.

    The earlier flap motor has a different 'cog' that is solid metal, and not hollow plastic like yours. Same shape though.

    The top flap motor socket does not appear to fail like the bottom one. I have not heard of a problem there. I believe it is because the bottom one is very close to the heater pipe and core which is always fully on and hot, so the plastic socket suffers heat fatigue even though the forces are low. The two work independently to do different jobs as does the one on the other side which is OK usually too.

    The idea that if you leave the controls alone when it is working OK, the flap will not be moved is a falacy IMHO because the computer is always adjusting things as the climate changes and the coolant temp changes.

    Good luck to other users of this thread.
    Jaahn
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  4. #4
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    A good attempt George and most helpful to have pictures. However, don't be too surprised if it snaps off. Despite appearances, the motor evidently runs until the flap stalls it and there is quite a lot of torque involved as the motor has reduction gearing inside. I have seen a couple of repair / extension efforts fail due to shearing off, so the material used is important. The motors are reliable, but the problem is simply the engagement in the flap spindle.

    EDIT: Thinking further on this, it may be that part of the reason for the shearing failures was that the flats of the extended peg and the damaged flap spindle end were not correctly aligned when reassembled. At the end of it's travel, the flap can obviously be well wound up.
    Last edited by David S; 5th February 2015 at 12:47 PM.
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  5. #5
    1000+ Posts George 1/8th's Avatar
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    Quote Originally Posted by David S View Post
    A good attempt George and most helpful to have pictures. However, don't be too surprised if it snaps off. Despite appearances, the motor evidently runs until the flap stalls it and there is quite a lot of torque involved as the motor has reduction gearing inside. I have seen a couple of repair / extension efforts fail due to shearing off, so the material used is important. The motors are reliable, but the problem is simply the engagement in the flap spindle.

    EDIT: Thinking further on this, it may be that part of the reason for the shearing failures was that the flats of the extended peg and the damaged flap spindle end were not correctly aligned when reassembled. At the end of it's travel, the flap can obviously be well wound up.
    Hi David,
    very interesting. There has to be something in the design to give feedback to the computer to tell it to stop turning the spindle. The only thing I can think of, which is often used in such applications, is a monitoring of the Amps being drawn by the servo motor. If they rise, the circuit should shut off, and maybe add a small amount of reversal to release torque. However I don't know which system is being used here.
    Anyway, upon closer inspection both of my shaft sockets have been split. As such, if my guess is correct, the motors will just keep turning beyond a flap closed position because the split will mean that the spline can just keep turning. The spline design has one flat side so it's possible to line up the motor shaft position and the flap socket correctly.
    The wood splint I have applied should be strong enough to stop the motor at the end of the flaps rotary travel, and so the amps should rise, and the motor stop... I hope. Otherwise I could end up with a broken shaft, which I really don't want.
    The only other system is one which uses a chopper wheel and sensor so the system can see what's happening. I couldn't see any evidence of those parts being used here.
    Should this also fail, there will be home made slots up and down my dashboard , with a simple lever and a knob on the end, the up position will be cold, the centre position will be normal, and the bottom position will be Hot. It will be mechanically set manually and the servo motors will be out the window.
    The first car my dad had which had a heater had a very simple arrangement which never failed. In the beginning of winter you simply turned on the tap under the bonnet so the heater water could flow. When the warmer weather came you simply shut it off.
    Cheers...
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  6. #6
    1000+ Posts George 1/8th's Avatar
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    Quote Originally Posted by jaahn View Post
    Hi George1/8th
    Thanks for your detailed fix with photos. That should help some people into the future

    A couple of comments to add from my experience for reference.

    The earlier flap motor has a different 'cog' that is solid metal, and not hollow plastic like yours. Same shape though.

    The top flap motor socket does not appear to fail like the bottom one. I have not heard of a problem there. I believe it is because the bottom one is very close to the heater pipe and core which is always fully on and hot, so the plastic socket suffers heat fatigue even though the forces are low. The two work independently to do different jobs as does the one on the other side which is OK usually too.

    The idea that if you leave the controls alone when it is working OK, the flap will not be moved is a falacy IMHO because the computer is always adjusting things as the climate changes and the coolant temp changes.

    Good luck to other users of this thread.
    Jaahn
    Hi Jaahn, I didn't know there was a version with a metal spline. In that case you would have to remove the servo assembly and saw a slot in the metal so you could get something to slot the "stick" into. That should work.
    Another way to splint this flap shaft COULD be to use a piece of spring wire or something like a large paper clip. This would be easy to work with, and would have some ' give '. However, if it had this springy 'give' action it might not shut off the servo. I'm just guessing because I don't know which method is being used in this design by "LE-Bureau".
    I don't think the lower flap motor is heat affected at all by those pipes. And because both flaps must be operating correctly to get the correct mix, I'm certain you must splint both control servos.
    At present mine are operating correctly. I can set either side to hot, and either side to cold, and both change. And change back again. All good now. See how long this lasts.
    Cheers...
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  7. #7
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    Hi
    I am no expert here but I think the operation of the flap motors is mis-understood. The point of having a computer controlled climate control is not to have things hard shut or hard open, but to have the computer monitoring the output temperature and modulating the two inputs as necessary to get the output exact as set by the controls.

    The two inputs are outside air, as is, or with a/c on, cold air, and the other is hot air from the heater core. The hot obviously varies from cool when starting out to 80deg normal running, and a bit higher sometimes. These inputs are variable so the flap positions will vary too to achieve the desired temperatures set. Actually this is just standard process control stuff but not usually found in cars before. Ahhh the wonders of computers !

    AFAIK there are three temperature monitoring thermistors in the air box, one below on each side, and one above for the screen air. I believe the computer probably applies a medium amount of flap in the direction it sees as needed, and then waits for feedback from the thermistors, as the result of this it applies a small correction and waits etc etc till the temp is exact, as computers always read it. This continues forever as the conditions change. The basic way to do this is programed in.

    I doubt the computer normally drives till the motor stalls, ever. The computer monitors all the currents from everything and applies correction as it sees changes. I believe it then remembers the "position" of the flap motor in a similar manner to the windows The only problem is when the flap does not respond to corrections as per the program in the computer, eg a failure of the drive socket.

    Here-in finishes the lecture
    Jaahn
    Last edited by jaahn; 6th February 2015 at 09:39 AM.

  8. #8
    1000+ Posts George 1/8th's Avatar
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    Hi Jaahn,
    a good description of the set up. As I said I'm not sure which set up is used on these systems. If the computer was controlling everything and stopping the motors when the flap reached the end of it's travel, there would not be a shaft with a big split in it. Maybe the system uses the sensors output/data reporting the temp. instead of the flap position. I'm not sure. I'm just happy now that the set temperatures are responding properly. They were not previously.
    Cheers... And I hope yours is good now too.

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