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jester77

Fogging sensor causing erratic a/c?

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I have a 2007 530i Touring.  I've noticed that my air con, despite being regassed in the last 18months, struggles to maintain a cool temperature when in auto mode - seems like hot air is blowing up towards the windscreen despite the a/c set to low.  On Max it works fine and is nice and cold.

 

Carly app shows a 9C55 error which seems to be the fogging sensor behind the rear view mirror.  My theory is that because this is faulty the car may think that the windscreen is constantly fogging and hence tries to blow hot air onto it whatever the a/c settings (as long as on auto).  Would that make sense?  Is the cure just to replace the sensor?

 

Anyone had this issue?

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That is one of the errors that keeps appearing on mine, I should get around to sorting it out at first it took a while to come back but it now comes back as soon as it is cleared. 

In other posts the replies have been along the lines of just ignore it but what is the point of having all the toys if they don't work?

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Yeah the error has come up previously when in for a service and they said to ignore it but I am pretty sure it is causing some a/c issues now so would like to sort as the weather gets warmer!

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Fogging sensor only tells the car to blow on the windscreen to demist it, it shouldn't have any effect on the rest of the system.

 

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34 minutes ago, GoNz0 said:

Fogging sensor only tells the car to blow on the windscreen to demist it, it shouldn't have any effect on the rest of the system.

 

 

Yes indeed.  But I think what is happening is that the malfunctioning fogging sensor is causing warm air to blow onto the windscreen even when I have the a/c set to a cool temperature, making it impossible to cool the cabin air (despite the dash vents blowing cool air).  If that makes sense?

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Yeah, my sensors are busted also.

 

Take climate control out of auto mode.

Run the AC manually only when you need it and dial temperatures as required.
A/C is only occasionaly needed in the UK so not a big deal for me.

Once A/C is switched on, leave on until 300m from destination, then switch off and open a window to dump any resulting humid air outside otherwise the wet air can dangerously mist up the windscreen during a journey.
 

Also, when its a hot sunny day, as I walk toward the car, press and hold the unlock button on the fob to fully open all the windows and vent most of the very hot air before you get in B).

 

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