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Discussion Starter #1
I have been having intermittent issues with my 159 1750TBi Ti's aircon for more than a year now.

The issues started when one of the aircon pipes rubbed through and all the gas escaped. The pipe was then replaced and I thought all was sorted.

Soon after, the aircon would randomly not work at all (the fans still blow but the air is not cooled at all). This will happen immediately on startup of the car. If the aircon works when you start the car, it will continue to do so. If it doesn't work on startup, it won't start working later, unless I switch off the car and leave it for 10+ minutes.

This happens once or twice a month at random times of day, during random weather conditions.

The car has now been with Arnold Chatz for a week and they can't figure it out. They also sent the car to an auto-electrician for two days with no luck. Currently factory reps are inspecting the car there too.

Any ideas??
 

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The aircon system is rather simple in that if the compressor clutch engages and there is enough gas in the system then it will work. Always. So let's assume that the gas pressure is correct. After all, the car is in the care of Alfa Romeo and that would be the first thing they check. Now: There are 3 switches which controls the aircon on-off though:

4-way pressure switch. If the gas is under pressure or over pressure or too hot or too cold then this switch interrupts the aircon. It is situated on the cold pipe from the radiator to the interior heat exchanger. Since the error is not consistent, it could be an intermittent fault, and most likely one of the contacts in this switch starts failing which causes the aircon to fail.

Failing that, the aircon compressor clutch relay may be slightly burned therefore failing to contact at some times. Replace the relay.

Finally and most unlikely, the aircon is fed from the ECU (don't ask me for pin numbers because I don't know) and when the car is under full load, the A/C switches off until load requirement is reduced. If this signal becomes intermittent it could be a failed or failing ECU but this is highly unlikely.

This process also assumes that there are no shorts on any wires inbetween.
 

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Discussion Starter #3
I took the car in last week whilst the aircon wasn't working, they checked and the compressor was running. Gas has been checked and replaced many times.

They have previously checked and cleaned all the electrical contacts and relays. They still haven't been able to diagnose the cause of this, but they decided that all they can do is replace the climate control unit/interface. I am collecting the car tomorrow morning, hopefully it is sorted now, although I remain sceptical.
 

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there is a valve inside the compressor. thats what failed on mine which had very similar symptoms to your car. that said i doubt the 3.2 and 1750 use the same comp
 
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