535i Heating issue

[Venus4NU]

I have searched these forums and can't find anyone who has had a similar problem.

My 535i doesn't always blow warm/hot air out of the front vents. However, it is always hot out of the defrosting vents. Shouldn't this be the same air? How can one be cool and one hot? I have the dials set to the warmest. I feel heat coming out of the defrosters but not the front vents - it's more of a cool air but not chilled. Sometimes I turn my car off and immediately start it up again and get warm air out of the front vents. It is either always warm or always cool, never changes mid-stream. Only thing I can do if it is cool is turn it off and start again and hope it is warm. At least 50% this works.

Please help our highs next week is 10!

[AutoXr]

The front vents are not designed to blow totally heated air. Can't imagine why. I keep mine shut in the cool Wisconsin winters. Kind of frustrating...I would really like nice hot air out those vents.

[Tiger]

Like he said... front vent is not designed for heat... and front vent always incorporate outside air. In winter, you can use defrost and bottom vent for heat... so keep bottom vents open and defrost to desired percentage of opening.

Too much heat out of defrost makes you sleepy and parched... so shut it off when not needed.

[PaulJ]

A reading of the owner's manual will detail the airflow and heat/cool distribution of the climate control system. It ain't what you think and needs diagrammatic explanation to visualize how it works.

Paul

[John B.]

My 535i blows nice hot air out of the dash vents above the radio as well as the 2 by the doors as long as the wheel is rolled to the hot setting. Which vents are you guys saying won't blow hot air?

[Claude]

I have searched these forums and can't find anyone who has had a similar problem.

My 535i doesn't always blow warm/hot air out of the front vents. However, it is always hot out of the defrosting vents. Shouldn't this be the same air? How can one be cool and one hot? I have the dials set to the warmest. I feel heat coming out of the defrosters but not the front vents - it's more of a cool air but not chilled. Sometimes I turn my car off and immediately start it up again and get warm air out of the front vents. It is either always warm or always cool, never changes mid-stream. Only thing I can do if it is cool is turn it off and start again and hope it is warm. At least 50% this works.

Please help our highs next week is 10!

You should be able to get hot air or fresh (cold) air or mixture of both from those front vents as well as from the center grid on top of the dash board. Proof of that : that's what you experience but erraticaly.

The control wheel in between the two main front vents (just above the radio and the OBC) is the one that control the temperature of the air of those vents and grid (tower the red spot for hot and the blue one for cold). This control wheel is attach to a potentiometer (variable resistor) that drive a step motor (electrical motor under the dash) that control the mixing trap that control the proportion of hot air and fresh outside air that will get in the car through those vents and grid.

The problem that you describe is probably due to bad operation of this mixing flap possibly because the step motor support is broken or the mixing flap itself is in bad shape (both weak points of the E34, two mecanical problem the first one easier to fix).

You'll find out here: http://bmwe32.masscom.net/johan/center_vents/center_vents_v1.1-3.html pictures showing the different step motors and the flaps. The picture under this title:
Now the heater box is out of the car you can start taking parts off so that the center housing can be removed from the box. show the step motor (the one just under the red tape) that control the mixing flap.

http://bmwe32.masscom.net/johan/ihka/ihka.html Motor #3 on the first picture here is the one i am talking about.

This step motor is not easy to reach but you don't have to dismental all the dash to see it and to reattach it. The procedure to reach the sword will also let you see this motor. It is located under the OBC right behind the three dials that control the left and right temperature and the blower speed.


Here is exemple alreay give on the board as how to fix broken step motor support (an other one).
http://www.bimmerboard.com/forums/posts/200205/

Hope this may help you to further analyse and perhaps fix your problem. Good luck.

[Venus4NU]

Sounds like I might have a broken flap. How mechanically savy do you need to be to fix this? I don't want to tear it apart and get over my head. I can change a tire, battery and alternator without a problem. I have even installed a simple muffler. Pretty much everything else is taken to the shop.

Yes, I always get heat out of the grill on the dashboard. The vents are the only thing that is sporatic. I know it is best in the winter to use the lower vents and defrosting vents BUT, my lower vents don't work. The previous owner told me they stopped working on him and he never had them fixed. (The only thing in my entire car that doesn't work!) When you move the slider to distripute heat to the lower vents you can tell there is no resistence of any kind leading me to believe the slider is no longer attached like it should be. It moves very freely. I can feel normal resistance on the defroster and dashboard vents sliders.

[Claude]

Sounds like I might have a broken flap. How mechanically savy do you need to be to fix this? I don't want to tear it apart and get over my head. I can change a tire, battery and alternator without a problem. I have even installed a simple muffler. Pretty much everything else is taken to the shop.

Yes, I always get heat out of the grill on the dashboard. The vents are the only thing that is sporatic. I know it is best in the winter to use the lower vents and defrosting vents BUT, my lower vents don't work. The previous owner told me they stopped working on him and he never had them fixed. (The only thing in my entire car that doesn't work!) When you move the slider to distripute heat to the lower vents you can tell there is no resistence of any kind leading me to believe the slider is no longer attached like it should be. It moves very freely. I can feel normal resistance on the defroster and dashboard vents sliders.

If a flap is broken i am affraid you can't avoid the big job, but 1) it's difficult to say for sure if it's the case or not (can't see it and it's difficult to test) and 2) the other cause (broken stepper motor fixture) is probably more likely and at least easier to check. So i would start going as far as i can checking if the stepper motors work properly.

If your lower / footwell vent flap does not work either it may well be because the stepper motors that control those flap (one motor for the left one and another for the right one) are either shot or their mecanical support broken.

I have on paper but do not have the web link of a diagram posted here by an other member (Bill.R) on the E34 1HKR1 control module) that show roughtly / schematicaly how the 5 stepper motors that control the different flaps are related to vent control sliders. Hope Bill would be able to put it here again for you.

The center slider (the one that control the amount of ventilation on the front vent and on the grill) is the only one connected mecanicaly (by a cable) to a flap.

Low mecanical resistance on the lower slider does not means that something is wrong, you don't have a mecanical link (cable) between this slider and the vent flaps but and electrical one (the slider controles the motor that controles the flap).

Temperature here to night (East Quebec / Canada) around -22C Brrrr...

[Paul in NZ]

i reckon there is something else wrong....i could,nt have the temp at max...its just too hot The IHKA sytem has the max tempa t about 26 or 28 deg C........