one_eyed_king: Just tried it in the car park and it reports a fault code of "22.1" - A/C Refrigerant High Pressure Switch, static open. (The compressor will remain off until the switch closes). This should be a warranty job anyway, but I hate going to main dealers blind. Does anyone know what a A/C High Pressure Switch is by any chance?
Dave N: The a/c high pressure switch protects the system from high presssures by opening at 35bar, but should then close again when it drops to around 28bar. What's interesting is did it just open, or did it see high pressures, open, then fail to close again? If the later, then obviously the cause needs to be determined rather than just putting a new switch on and hoping for the best. Usual cause of HP is fan failure.
one_eye_king: Thanks for that, Dave N. The reason I asked was because I was wondering if the recent very hot weather had overstressed the system in some way.
When you say fan I assume you don't mean the engine cooling fan?
Forgive my ignorance.
Dave N: I do mean the engine cooling fan. There are 2 of them, and they run at half speed all the time the a/c is on. The more load on the system, the higher the high side pressure goes. If it reaches 17.5 bar, then both fans go to full speed. If the pressure carries on going up (which is very unlikely), then the HP switch cuts the whole lot. When this happens, the pressures subside, and the whole lot turns itself back on when it drops to 28 bar. If there's something wrong with the system, then the pressures shoot up to 35, it cuts off, and so on. You will normally notice this happening as it will cycle every 3 or 4 seconds, jolting you about as it bangs on and off, loading then unloading the engine.
As I said before, pressures will only normally get up this high if the fans fail, though it can be caused by too much refrigerant in the system, and only show itself when it gets really hot. It may be the switch has just plain broken, in which case none of the above applies, but as the switch is actually a 3 position switch, that opens at low pressure, closes at normal pressure, then opens again at high, it seems a bit odd that it has failed on the HP part, whereas one would expect it to fail to the low pressure setting. That's why you just need for the dealer to check that it's a straight switch failure, and not one preceded by a high pressure situation, otherwise you'll be back there again with poor a/c.
![[:@]](/forums/styles/seatcupra/oldforumsmileys/furious.gif "Furious [:@]")
