Air con - suddenly blows hot air - Alfa Romeo Forum
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Air con - suddenly blows hot air


My 2000 model 156 Selespeed has suddenly developed a weird tendency to blow hot air into the cabin at random intervals after 7 years of quality service.

I'm happily cruising at motorway speed with the temp set to around 19c - all is well - I'm getting nice coolish air at the temp I would expect.

Suddenly the cabin starts to heats up with hot air. I have to override the a/c temp down to low to get icy air back into the cabin. Then I edge the temp back up to close to 19 and leave it. All is well for a while before the process happens again.

Outside temps about 21c mark when this was happening.

Just had a new rad/coolant expansion tank along with timing belt service as car was overheating due to leaky rad. Air con gassed approx 2 years ago.

I have always driven with air con compressor (snowflake) on, apart from a few times recently when the car was overheating (and prior to rad problem being identified), when I turned the compressor off, and the temp/fan on high to 'cool off' the engine!

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Re: Air con - suddenly blows hot air

Dunno mate really!: Temp sensing thermistor malfunctioning? Bodger and Nev are resistor, thermistor, diode,transistor, capacitor, etc. etc. guys, who may help. or ALincs?:
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Re: Air con - suddenly blows hot air

Next time it happens check the outside temp reading. The exterior sensor (in the wing mirror) may be faulty which would show a big minus figure. Regardless of the temp in the car the aircon goes a bit screwy if it thinks it is -23 outside!
Also, if you have the time, take the centre panel off and clean the internal sensor which I *think* is behind the little 10p sized grill to the left-ish of the aircon control. They tend to get fluffy over time. If you can`t be bothered to disassembled, give it a blast from a can of compressed air through the grill.
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