The a/c system cools at a pretty much fixed rate, so to vary the temp you turn the knob on the dash, and that will cause the compressor to cycle on and off at a different rate. Slow rate = compressor on more time = colder.

The knob has an orange part near the farthest point to which it will turn. This area is where the evaporator might freeze over, something to be avoided. It will give you max cooling, but do not leave it there long.

See if the on-off cycle changes as you set the knob at different locations.

Also, have a look into the sight glass. Find it near the receiver/dryer which is at the right end of the radiator and has the low pressure switch mounted on top.

The glass may be dirty, so wipe it clean and look in there while the compressor is running. If you see soapsuds, the freon charge is low. If you see just a few bubbles now and then, the charge is OK. Low charge can cause fast sysling, too.

Replacing any component which requires opening the freon system can require a new freon charge, another thing to be avoided.

Good Luck,

Bob

:>)