2019/12/05

How to fix no HEAT from the central vent on BMW E36

One day I've found there was no heat air from the central vent,
so I spent some time checking it out.
I checked the Water Valve first.
Since it's a refurbished part and installed a couple years ago,
it's still clean inside and worked fine plugged with 12V battery [Pic 1].
Remember NOT to break the wires when assembling the part.
I also replaced the new Connection Flange and O-rings (EPDM) of the water valve [Pic 2].
When I tested for the first time, 
there was even no hot water in the water valve hoses. 
So I tried to bleed the radiator afterward.
After that, I got heat air from the side defog vent,
but there was still no heat from central vent.
I was so so frustrated.

I started to study all the documents about E36 IHKA and IHKR,
and I found there were flaps inside the air conditioner to mix the cold and heat air.
So I took off the cover under the steering wheel,
and tried to find where was the mixing flap motor (actuator).
I could feel the motor running when I turned the mixing dial,
but the flap didn't move at all.
I guess there must be something wrong with the motor.
However, I spent hours studying how to get it off.
Lastly, I followed what Bentley service manual said,
and just pushed the "CLIP" on the motor [Pic 3].
Luckily, I took it off and unscrew it to check it out.
It seemed that the shaft was pushed out too much [Pic 4],
so I knocked the shaft to push the gear inside.

After restoring all the parts, 
I got heat finally.
It was quite a journey to find out the answer to the heat.

[Pic 1]

[Pic 2]

[Pic 3]

[Pic 4]

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