[american-kiwi]

if the valve is working..then it should be freezing cold right at the outlet line from the valve to the evaporator (a/c heater box)...because the liquid 134 is buiding up in that line from the dryer to the valve...and if there is a small amount getting out (valve opening)...thats where the pressure drop is...then the liquid turns to a gas and freezes up...feel all the lines...the line from the A/C pump to the condenser should be hot.....all lines after the expansion valve should be ice cold...so feel the line going into the pump...ice cold?....if not...then that side is where the problem is...and also for the line coming out of the pump...should be very hot...if not..problem with the pump...the pump has 2 jobs...heat up the 134, and pressurize it,...hope that helps you a little...i work on corolla's all day...LOL (toyota tech)
PS...did he top up the a/c oil?....both for the pump and the condenser...every part of the system has a set amount of oil in it
if you hook up the pressure gauges
the high side (red) is should read about 220-330psi at 90f outside...the low side (blue) should be around 15-25psi