Having the same problem you originally described. It's 87F ambient temp and the unit is blowing about 60F - 64F air on the left side, but feels like ambient or even a bit like heat on the right side. Checked pressure and I've got 40 psi on the low side (35 before it gets hot, and jumps to 70 when I cut it off). I tried adding some 134a, but it won't take any. Weird. Really makes the most sense to me that it would be the heater control valve(s), but then I read your story about how adding the 134a fixed it. Confused. Thinking about blocking off the valve and/or heater core to prove if it is the valve or not. I know in other domestic vehicles for decades in the past folks would do this, and I have done it myself, too. I knew one guy who installed just a standard gate water valve in place of the heater control valve, and he just raised the hood and opened/closed the valve whenever he wanted air or heat.