kd7iwp

Looking at this diagram you can see part 10 carries air from the heater box to the rear vents and it is all one tube, from one source. How then does the temperature control knob work for the rear seats? Part 11 (the rear vents) do not appear to have a bowden cable so I don't see it opening/closing a flap anywhere. Obviously the control knob for air flow simply opens/closes the vent grill itself, but I don't see how the temperature knob can functionally do anything. Does it do anything?

audiophool

I don't spend time in my back seat, but suspect the knob controls a damper in the HVAC box that alters the temperature in the same way iDrive adjusts the temperature to the face-level vents. This, however is a WAG*.





*wild-assed guess

scottalexander

Wild ass guess #2

The driver and passenger (up front) control the heat temperature.

The person in the backseat can use the scroll wheel (red setting) to receive the same heat temperature settings from those in the front.

If the person in the backseat that it was too hot back there, and just wanted recirculated air or fresh air they would use the scroll wheel (blue setting) to block the hot air coming from the driver settings.

kd7iwp

The problem I have with the first WAG is that I don’t see any Bowden cable or electrical connector for the rear vents, so how would IHKA get the signal? For WAG #2 there is only one pipe running to the rear vents. I do believe you are correct that whatever the face-level dash vents in front blows out is what comes out the rear, but with only one pipe how else would the non heated air get to those vents?

scottalexander

Wild ass guess refined:

The driver and passenger (up front) control the heat temperature.

The passenger in the rear seat operates the scroll wheel to regulate the amount of hot air they want to the back seat.

If they want, they can use the wheel to cut the hot air off. That is, they just turn the wheel to the blue setting.

The scroll wheel in the back seat is just regulating the volume of hot air going to the back seat (that's already been defined by the driver).

Now let's look at summer:

The driver puts on the air conditioner and sets the temperature.

The person in the back seat adjusts that scroll wheel (just the blue section now) to regulate the amount of air conditioning coming to the back seat.

If its too much, they use the wheel (in the red section) to cut off the volume of cooler air.

This rear seat scroll wheel, gives the person in the back seat the fantasy they are in control of the temperature, but in reality they are only in control of the volume.

kd7iwp

That’s more along the line of what I’m thinking. Just seems silly that there is then an additional wheel to adjust the air volume. I wonder how difficult it is to remove the air vents. Really that’s what I should be doing to answer my question. I did notice the other day while driving that I could feel air emitting from the vents regardless of the hot or cold position. It didn’t really feel like the air temp changed much (though I generally keep my face-level vents at a neutral temp).

audiophool

I'm sure BMW wired it into the IHKA somehow. Since it's -10C today, maybe I'll try it later.

kd7iwp

I’m thinking you’re right. I watched some disassembly videos and there is indeed an electrical connector going to the vents.

scottalexander

Yes, there is a electrical connector in the rear of the scroll wheel. See below.

Now the question is, does it actually work?

audiophool