Air con constantly blowing hot

[Overweight Unicorn]

Evening all,

As per the title, the air con, once the engine is to temperature will only blow hot air out, irrespective of what the temp contollers are on.

Any idea of the root cause or how to fix?

TIA

[Nictrix]

Is it from all vents or just the ones in the middle of the dash?
The ones in the middle of the dash have their own adjusting wheel for temperature that is separate from the main control.

[deltasierra]

For me the first action would be to check the gas in the aircon system most garages will check that for £60-80

[Pondrew]

For me the first action would be to check the gas in the aircon system most garages will check that for £60-80

There is an easy way to check yourself if the a/c is short of refrigerant as long as the compressor runs:

Turn the a/c on. Look at the end of the compressor to make sure the clutch is engaged and spinning. After a few seconds feel the temperature of the larger of the two easily accessible a/c pipes (it is on the right side of the engine bay looking at it from the front). That should feel cold, really cold.

If the pipe feels only cool or warm the refrigerant is low. Chances are that the compressor will 'cycle' quite often aswell in this scenario and the electric fan won't run.

The above presumes there is enough refrigerant for the compressor to run. If it is completely empty the compressor won't run.

[B21]

If it’s blowing hot air out of all vents then it’s usually the temp sensor or control ECU..if it’s out of one vent it’s the stepper motor..

As usual first port of call is to read the codes with a decent BMW specfic fault code reader..

[matsmith749]

Fairly recent purchase?

Make sure the wheel under the vents is set halfway so you can see blue&red. If all you see is red, you get warm air no matter what you have the temp dial set to.

[matsmith749]

Fairly recent purchase?

Make sure the wheel under the vents is set halfway so you can see blue&red. If all you see is red, you get warm air no matter what you have the temp dial set to.

[Overweight Unicorn]

Thanks all.

To answer some of the questions, I've had the car (2011 23i) for over four years, but a I live overseas so it gets very little use other than my daughter taking it around the block once a week.

It blows hot out of all vents.

A Mechanic believes that a valve/flat has wedged open, but would need to remove the dash to be sure. For me though, I'd only expect one side to be affected if this were the case.