How do you change A/C expansion valve on a 95 avalon

[RMoore]

Hi all

I Think my expansion valve may be bad, Does anyone have a step by step procedure or at least a good overall steps to get me started. Here are my symptoms

1995 Avalon with an Air Conditioning problem: Problem: A/C will start taking a charge, the temp will start to drop at the center air vent but no much. As I give it R134 pressure at the low side will start to build. if I stop at 15 Lbs at the low side the center temp will be about 60 degrees. If I tweak it little at a time with temp will drop a little lower, about 58 degrees. As soon as I reach above 17 lbs on the low side. pressure will start to rise and then the high and the low side will start to pulsate. the low goes up to 60-70, back down to 20, back up etc at a rapid cycle and you can hear the system making sounds like a hooting sound. I have a vacuum pump and reservoir, if I pull the system back down abd start over I get the same symptom. If I leave it at around 15 Lbs on the low side it stays working but not very cold.
On the high side.
At 15 lbs on the low side and the pressure NOT cycling, the high side is a 350 lbs, if I add a little more to bring the low side to about 17 lbs the high side goes to 400. Add any more and the cycling starts. The high side goes from 400lbs to above 500lbs ( pegs the meter) and down\up etc.
The compressor is kicking on. I think it may be the evaporator but hate the idea of changing it if I am wrong, Anyone have any other idea of something else to check before tackling the valve.

Optional Information:
Year: 1996
Make: Toyota
Model: Avalon
Engine: 6 cylinder

Already Tried:
Pull Vacuum on system and charged, Added oil. Replaced Drier, inspected lines for kinks as well as I could.

Thanks Ray

[The Digital MagE]

there was another guy on here that just did this - apparently without success. he was complaining about pulling the dash out... or out from under the dash... it didn't sound like anything i would like to try!