C8 Air-Con not working in very hot weather!

[brittleware]

There have been two occasions recently when the temperature here in Surrey, UK, rose to the high 20s. On both days the aircon in our Fiat Ulysse (A C8 / Peugeot 807 under the skin) stopped working. Otherwise it works beautifully on cooler days. Is there a sensor I don't know about?

The last re-gas about three months ago included dye - my black light shows nothing unusual, so I think it's fully charged.

[myglaren]

Any chance the coolant was overheating?
With engine overtemperature the aircon will drop out to remove the load from the engine and allow it to cool down.

[oneday]

could also be inoperative condensor cooling fan, air in system causing high pressure trim, moisture in the system blocking the filter dryer, just a few things to look at

[brittleware]

On both occasions, the air-con didn't work on start-up and the engine temperature was always normal at about 80c. Two large fans working normally.

Obviously higher temperatures will lead to higher pressures in the circuit. Is there a high (over) pressure sensor somewhere? As I said, it has only ever failed to cool when it's seriously hot outside... (Just when it's needed.)

[oneday]

there should be a high pressure switch it may have been overcharged

[brittleware]

Thanks - I'll consult SEDRE and see if I can locate it. The garage who charged it are pretty good (an unusual thing for me to say) so I'll get the pressure checked out too...

[oneday]

anyone can make a mistake wrong charge of gas wrong gas any number of things it could be. just seems to me to be pressure related as it only happens on hot days when it will cause the pressure to be higher also check the outside of the condensor is clean and has good airflow.

[addo]

If the blower fan doesn't work (in addition to the AC), it's probably the fan controller that's carked. Cheap enough to fix.

[brittleware]

Understood - but the blower fans have always worked perfectly, both front and rear. The A/C works brilliantly when the air temp. is below about 26c, which would seem to indicate that it's a little overcharged... I do have a gauge, must get to check it out. (Currently preoccupied by silly intermittent engine temp. readings even when engine cold - checking sensor and connections.)