A/C? where for art thou?

[Ivan Tuma]

yes, there is a switch in the system that prevents the comressor clutch 
from engaging
when the system is too low on coolant ... simplest test is to find the 
fill or purge valve and
quickly depress it ... if there is a loud, powerfull hiss, chances are 
there is some freon still
left in your system however; if there is a fizzle ... you need new 
freon. at about $60 to $80
per lb of the old R12, it will probably cost anywhere from $150 to $200 
to get it serviced...
barring any leaks in the system.

ivan