Took my 74 Monaco wagon to my son's to see if we could get the A/C working. Sucked it down and it held a vacuum so we charged it and it works great! It had already at some time been converted to 134 so that's what went in. Now pretty much everything works on the car. Oh, and ambient temperature was 72 degrees.
I did have to go back to the stock wheels and wheel covers because the front tires on the chrome wheels are a little old and didn't ride smooth. Luckily I like the stock look.
Yeah I feel like I won the lottery on this one. You almost never get that lucky. Sellers always say "Just Needs Charged" but that's almost never the case.
Yeah, I believe the entire system underhood is good, but all of the H-Vac stuff under the dash is vacuum controlled and it ceased working decades ago.
Although, I did get the A/C system on my F-100 converted to 134 and charged up a couple of summers ago and it works great. So, I guess I can't complain.
The rule of thumb I learned is this: interior temp equals ambient minus forty degrees. Forty degrees is the most temperature you want it to drop, while preventing ice-over in the system. Some newer systems have ways to detect ice-over, and cut the compressor clutch engagement until the temp raises up enough to re-engage the clutch. So, your wagon has a 39°F drop, and that should be verified at full load (all doors open).
Most of the time I found that loss of charge was due to hard seals the only things I changed on the 85 were the o-rings and expansion valve.