[blessthearma]

This summer, I bought a beautiful 2006 BMW 330xi. Now that temperatures here in Italy are dropping below 0°C, I’ve noticed an issue: the passenger side of the car doesn’t heat up. Even with both zones set to maximum heat, the passenger side blows freezing cold air, while the driver’s side works perfectly and blows hot air. I’ve also checked the climate control wheel and tried setting it to both cold and warm, but it didn’t fix the problem.

For reference (in the picture): the areas marked in red show where the cold air is blowing. On the windshield, the air blows half warm and half cold, so only half of it defrosts. What could be causing this issue?

[NZE90]

Can you read the fault codes of the vehicle and post them here?

[blessthearma]

Originally Posted by NZE90

Can you read the fault codes of the vehicle and post them here?

Will post code this weekend, but since the driver’s side blows hot and cold air as it should depending on the setting, I suspect the passenger side thermostat might be broken. How difficult is this to fix as a DIY project?

[gbalthrop]

Originally Posted by blessthearma

... 2006 BMW 330xi... the passenger side of the car doesn’t heat up. Even with both zones set to maximum heat, the
passenger side blows freezing cold air, while the driver’s side works perfectly and blows hot air...

Most common cause of one side NOT responding to T-stat setting is an issue with the "Mixed Air Flap" on that side
(Right or glovebox side in your case). If you had INPA or ISTA (BMW diagnostic software), or a Scan Tool that can display
Flap Positions, or other INPUTS to the IHKA Module, such as T-Stat settings, diagnosis would be quicker & easier. I will
attach ScreenPrints from INPA showing T-Stat settings & Flap Positions, from my 3/2007 build 328xi, along with
ISTA wiring & Right Flap Motor (M154) Location. "0" Mixed-air Flap positions shown is full cooling, both sides, T-Stats 68F.

If you are able to get INPA or ISTA, & you have a Windows Laptop, you will be able to diagnose most anything, with Forum help.
ISTA wiring diagrams, component locations, & Repair Procedures are also quite helpful. First step in ANY Diagnosis is to
CORRECTLY understand HOW the system works. The attached ScreenPrints should help you understand Flap function.

There are some tests you can do without a Scan Tool/Software, with warm engine, so heater core is > 70C. First Concept:
There are TWO "Mixed-Air Flaps", Left & Right. They determine how much of the cold air that has been cooled by the
Evaporator/Refrigeration coil is sent through the Heater Matrix. "0 %" is full-cooling, NO air directed through Heater.
100% is Full Heat, ALL air directed through Heater.

1) Realize that the various IHKA Controls SHOULD activate flap motors & take time to identify which flap(s) each button
controls. e.g. "Defrost" button on right side of IHKA panel over-rides other settings: Both Mixed-Air Flaps send ALL air
through Heater Matrix, AND all/most air is directed to the Windscreen vents.

2) The buttons on the Left side of the IHKA panel control Vent Flap Motors: Windscreen, Facia, Footwell.

3) The T-Stat settings provide Input to IHKA Module for Mixed-Air Flap modulation of Vent Output Temperature.

4) "MAX" button in center of Left T-stat over-rides other settings to provide Full Cooling.

5) The LIN-Bus (Green wires shown on ISTA SSP wiring diagram) are in Series, so that a wiring fault MAY affect all
other Flap Functions "Downstream" (to right on SSP) of that fault.

So testing button function, waiting up to 30 seconds for flaps to respond, listening for whir of motors & feeling air direction
& Temp, can allow substantial diagnosis, IF you understand system function.

Please let us know what you find, & we can suggest "NEXT Steps".
George