I had my '91 Vanagon worked on by a general mechanic who found
several leaking seals. He recharged the system with R-12 in spite of
the fact the system had been converted to R-134 and had been worked
on by three other shops who had various degrees of expertise ranging
from little to a lot.

The system is working very well putting out 32 degree air at the
front discharge vents (I drilled a small hole right above the vent
and inserted a 2" dial thermometer) with the fan set to 2 and full
cooling. On really hot days the system will drop the air about 40
degrees from ambient depending on the sun load and the humidity. If
humidity is high I may have a problem with evaporator icing.

Be certain the system is complete free from leaks, a good extended
vacuum is pulled and the correct amount of refrigerant is installed.

Herb