Chassis a/c failure

[jwasnewski]

Need help from the a/c guru's, please. I prepared to convert my chassis
air to 134 because my system abruptly quit blowing cold air, it is
winter, and a/c guys need jobs. I figured that the R-12 had leaked
out. Put the guages on the system all was well, the compressor, dryer,
condenser, and hydraulic fan were operating as advertised. Cold and
hot lines at the compressor but no cold air at the cockpit through the
evaporator, fans blowing ambient air. The technician concluded a bad
expansion valve. Of course it is in a, well some of you know where it
is.
Could anything else be the culprit? The slide thermostat at the pilot
control? A low pressure valve(probably not)? Such is life, and easy
job turns into a pile of ----.
Thanks,

Leroy Eckert
1990 WB-40 "Smoke N Mirrors"