e34 Fan System

[porterrico]

Hi everyone

i was just wondering if anyone could help me with a problem with my e34 (520i) fan system. the main blowers only blow cold air but the other two (under the screen and under the dash) blow warm air. i have no idea what i could be and i am freezin when i drive :)....... HELP!!!!!!!!!!!!!!!!

THANKS JAMES

[shogun]

Hi James,

can you give us some more information on your system, such as with/without aircon,
how is the setting of each wheel at the control panel when this situation appears.

[Qsilver7]

do you have an owners manual? it so, it will help you understand the HVAC system...it has something called "stratified" air distribution. This allows you to blow hot/heated air to the floor and windshield...but also allows you direct warm or cooler air to your face (dash vents) to keep you alert of from becoming sleepy (hot air in the face can do that). The dash vents have another reostat controler (dial) in the middle of the center dashh vents...do you have that dial turned toward the "blue" dot...if so...then cool air is going to blow out of the dash vents. The "red" dot will allow you to select warmer/ air to blow out of the center vents. You may also want to shut off the vent at the rear of the center console...it only directs fresh air or cooled "conditioned" air to the rear passengers...rear passenger receive heated air thru the floor vents under the front seats.

(in case you don't have an owners manual)
http://memimage.cardomain.net/member_images/7/web/739000-739999/739005_8_full.jpg
When you read the owners manual...you'll see that, for heating, it suggests using sliders #1 and #3 (windshield & floor vents).
http://luuk.xs4all.nl/bmwboeken/bmwe34manual/pg30.jpg
http://memimage.cardomain.net/member_images/7/web/739000-739999/739005_29.jpg
http://luuk.xs4all.nl/bmwboeken/bmwe34manual/pg31.jpg

[ra_pro]

I may have the same problem. For me dial/control for the dash vents makes no difference . It always blows cold air whether it's on blue or red. What needs to be checked?

[Anthony (M5 in Calgary)]

I may have the same problem. For me dial/control for the dash vents makes no difference . It always blows cold air whether it's on blue or red. What needs to be checked?

There's a stepper motor that controls the temp of the upper vents. Its bracket is flimsy and breaks off due to the torque from the stepper motor. The motor then cycles out of its operating range due to the nature of the design. Temperature cannot be controlled at this point.

Here's an ugly but effective repair - viewed from inside the glove box area, directly behind the radio/OBC.
http://img.photobucket.com/albums/v11/interalian/temp/ventstepperfix.jpg

[porterrico]

Cheers for the help i managed to get it working thanks to you all helping me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!! now i can take my coat off in the car ha ha

[Jay 535i]

Cheers for the help i managed to get it working thanks to you all helping me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!! now i can take my coat off in the car ha ha

So, what was wrong?

Anthony, can you explain a little more what we're looking at there?

[VentoGT]

OK, reviving an old thread. Now that it is starting to get cold, I realize that my stratified air vent in the center is not working; it blows cold when I have the AC on and hot when I have the heat on but it only blows in conjunction to the temp dialled in, regardless of the warm/cold knob in the center of the dash.

On my e46, when I move this from warm to cold, there is some resistance. In the e34, the wheel gives no resistance at all. Could it be the stepper motor bracket issue? Thanks in advance.

[colo525i]

Hate to hijack this thread, but are the red and blue dots supposed to be lighted? i could have sworn they lit up when i first got the car.

[Yiorgos]

You mean these?

http://memimage.cardomain.net/member_images/7/web/739000-739999/739005_29.jpg

Never were lighted on my car...

[jbourke]

Hi everyone

i was just wondering if anyone could help me with a problem with my e34 (520i) fan system. the main blowers only blow cold air but the other two (under the screen and under the dash) blow warm air. i have no idea what i could be and i am freezin when i drive :)....... HELP!!!!!!!!!!!!!!!!

THANKS JAMES

Are you sure you have a temp dial between the main blowers? My 520I hasn't, only cool or cold (aircon) air from them. Which is a good thing keeping the driver awake as mentioned.

[DaveVoorhis]

Hate to hijack this thread, but are the red and blue dots supposed to be lighted? i could have sworn they lit up when i first got the car.
I could have sworn mine used to light up, but they don't and now I'm not sure they ever did. I also thought my seat heater buttons had a green telltale, but they definitely don't -- they light up bright orange when activated. I suspect my, uh, what do you call it...? Memory! That's it! ...Is failing. Or somebody swapped my car for different one when I wasn't looking.

[Anthony (M5 in Calgary)]

I could have sworn mine used to light up, but they don't and now I'm not sure they ever did. I also thought my seat heater buttons had a green telltale, but they definitely don't -- they light up bright orange when activated. I suspect my, uh, what do you call it...? Memory! That's it! ...Is failing. Or somebody swapped my car for different one when I wasn't looking.

If your control knob has the coloured dots per Yiorgos' picture, they don't light. Earlier cars with recessed red and blue dots in the frame are lit - they only have a white stripe on the wheel that also illuminates thru fiber optics.

[Claude]

There's a stepper motor that controls the temp of the upper vents. Its bracket is flimsy and breaks off due to the torque from the stepper motor. The motor then cycles out of its operating range due to the nature of the design. Temperature cannot be controlled at this point.

Here's an ugly but effective repair - viewed from inside the glove box area, directly behind the radio/OBC.
http://img.photobucket.com/albums/v11/interalian/temp/ventstepperfix.jpg

Anthony, were you able to install that bracket through the glove box opening, or had to remove other parts of the dash ? The main problem to fix those steep motor breaken support is to get access to it.

[DaveVoorhis]

If your control knob has the coloured dots per Yiorgos' picture, they don't light. Earlier cars with recessed red and blue dots in the frame are lit - they only have a white stripe on the wheel that also illuminates thru fiber optics.
I've got the older style control knob, and nothing lights up. I've also noticed that my temperature and fan knob backlights have gone out, and only one of the vent sliders lights up. Time to go hunting for bad bulbs and grounds.

[KenB]

My red and blue dots do light up.

I also have a bulb out behind the 3 control knobs, looks like kid of a pain to get to, radio, OBC and heater controls all have to come out to get to the bulb. The heater control panel is the part I don't like the looks of messing with as one of my sliders does not return all the way to the left but still works, I don't want to make it worse.

[Mike-AZ]

A couple years ago, I could only get cold air out of the center vents on my '94 540i. I have the system with the stepper motor and the "knurled wheel" that lights up. Not only was the stepper motor broken out of it's mount, which required a thorough epoxy reset, but my knurled wheel was also defective...probably due to worn contacts. I ordered a new center vent / dial from the dealer. It comes as one whole part. I don't think it was expensive. -- Mike

[Anthony (M5 in Calgary)]

Anthony, were you able to install that bracket through the glove box opening, or had to remove other parts of the dash ? The main problem to fix those steep motor breaken support is to get access to it.

This repair was made through the glove box but I may have removed the radio as well. I drilled through the stepper motor's gearcase housing screws and used long threaded rod to secure it to the one remaining tab on the HVAC box. The fabbed up bracket was made to constrain the stepper at both ends of its travel. With the gear reduction in the stepper assembly, it can generate large amounts of torque - that's what breaks the mounts or pops the motor out of the HVAC housing. If the stepper has been operating without constraint for a while, it will be well out of alignment. You can get it back in sync by manually restraining it at one end of its travel using pliers. Once the stepper has "homed" a few times it will reset to the original range. My fix was done about 5 years ago and is still working.