Okay,

For the first time in a long time today the weather has warranted the use of some air-con.

Basically what happens is that the clutch engages for ~10seconds, the air in the cabin chills with a hissing noise and then the clutch kicks out.

The air temp comes back quite warm again over the next 10 seconds and then start again.

Is this normal?

I walloped a pressure guage on the low side and was watching the pressure as it's doing this. The pressure guage is a fairly cheapo one that has green/amber/red zones on it and I wasnt paying that much attention to the actual pressures - basically the guage would slowly drop until it hit the interface between 'good' and 'low' - the system would kick out and the pressure would build back into the middle of the 'good' area.

The aircon was kicking in and out at exactly the same pressures every time - is this normal or should the compressor be running permenantly?

Should I be looking at the pressure sensor switch?