Bmw 318 air conditioning tx valve

the expansion valve (TX) valve is on the inlet side of the evaporator under the dash (air conditioning)

Are you sure that the belt only turns the AC compressor? Be sure that it's not also connected to the fan and the power steering pump. If it's only turning the air conditioning compressor then you can live with it for as long as you can live without air conditioning.

Try checking the condition and operation of the following:
1) Spark plugs, leads and coils2) Fuel filter and pump3) Air filter.4) Idle control valve.

Check coolant level first. If coolant is ok. Check under hood petween engine and salon is heater hoses connected with heater valve check it is it worcking.

Fuse 48 40amp controls air con
Located under dash driver side below steering column

most fuses are in the fuse box under the bonnet at rear left side but there are some fuses under the dash lower panels on both sides.

There will either be two torx bolts behind the steering wheel spokes to release the airbag or in the same place there will be a hole on either side where a flat head screwdriver can be inserted to push a spring clip off a securing clip. Remember to disconnect the battery before touching the airbag. Once the airbag is removed you will easily be able to undo the bolt that retains the steering wheel.

The Anti-theft control module is behind the glove compartment the transmitter/receiver module is under the left dash panel.

dimmer switch is on the dash on your r/s and must be replaced

Being a 2006 BMW, I don't know if you really want to tear into the dash compartment. Your AC is working fine, the problem with the unit is your heater control valve under the dash is faulty. you cant fix it but replace it the cost with single solenoid 85 bucks and dual solenoid is 172 buck; your would have two because your car equip with his and hers climate control; without proper tools to work on the car taking the dash apart is a task especially you have to know every bolt location. The unit is not adjusting the valve like it suppose to. The valve work like and normal valve, same as your faucet at home on or off. the valve is not shutting off fully due to solenoid faulty or the valve it self is stuck,jam or not sealing and that is the reason why you still getting warm air. I can assure you if you turn the ac button off and let the fan run only you will get nothing but hot air, the air seem warm because is mixing with with the cold air from your evaporator. hope that help some, good luck