Quick Cool took the whole system apart. Pressurized and checked for leaks in the evaporator, suction and discharge lines, condenser, drier. Ended up being the nose seal for the compressor that they replaced.
After some talk of flushing, they pulled out a large bottle they claimed was nitrogen. Used it - without any solvent - to "flush" each part. Held pressure at 300 psi for a few minutes after they installed a new drier, then pulled vacuum on both high and low sides of the assembled system (with a real vacuum pump) for about 12 minutes. Broke the vacuum with refrigerant, charged up the system. Evaporator discharge line temperature is 19°C when stationary, lower than that whilst driving; I saw 4°C at the lowest during the day. It only reached 0°C at night, causing the thermostat to trip.
It's "working" so far. The compressor has developed a faint whine that I can hear at around 4000 rpm. I fear it will need replacement soon. The condenser and evaporator have the older R-12 fittings on them. The TXV was not replaced and is still hissing away.
