Haywire R12 Pressures

[Joes4x4Ranger]

I just overhauled my R12 system in my 1991 splorer. I changed compressor, orifice tube, accumulator, Vacuumed the system down to 30" for 2 hrs.

I charged the system with 32oz of R12 like the Clymer manual lists. I weighed the R-12 in with a digital charging scale. When I was done I took it for a drive, clutch kept cycling and center vent temp was like 60*.

I hooked my gauges up this mourning around 9am ambient was at 96*. The clutch kept cycling every 10 seconds and I could not get a steady pressure. I added a little R-12 to get the low side to about 30psig and high side to about 250psig center vent temp was 41*. The truck sat in the sun for several hours, I then drove it and it did not cool properly.

I hooked the gauges back up and F#$k!!!!!!!! Ambiant temp was 112* low side pressure was up to 50psi and High side up to 325psig. Why would there be such a huge increse in pressures in just 4 hours. Did I over charge the it BIG TIME??? I only added 3-4oz more just to keep the clutch from cycling.

 

[ranger7ltr]

Few more variables in this mix...

First was the system sealed but just not working before the overhaul? How much oil is in the system? Was the compressor replaced due to black death? Was the condensor blown out and the flow through the core verified?

Your pressures were good for the ambient temps but I wonder what condition the cooling fan\clutch\condensor?

Since you charged by weight, I am wondering if there is a restriction in the condensor stopping the transfer of heat from the refrigerant through the condensor... Your fan and fan clutch can only remove so much heat; Use a garden hose to run water across the condensor and see if the pressures and vent temps drop...

 

[Joes4x4Ranger]

The R-12 to 134a conversion was botched when I got the truck. The oil was not removed correctly and thrashed the system. I'm EPA certified and can get R12 so I decided to put the system back the way it was designed. Putting R134a into a R12 system is mediocre at best.

I flushed the system with A/C flush from autozone followed by a little Mineral spirits. I kept flushing till all solvents came out of each component clear. The system blows MUCH colder than my previous Explorer with a R134a retro-crap.
At the 112* ambient my system blows 39* air when I'm moving and 50* air at a long stop light.

It has been a long time since I used R12 and I thought the pressures seemed high for it. I thought R12 was like 2X ambient + 15% that would give a High side reading of 250psi-260psi@112*ambient. Mine was 325psi. I went back out and recovered enough to get the high side to 275psi @ 1500rpm@ 112* ambient. That took the low side back down under 30psi.

I'll see what happens when the temps are under 110 if the the clutch cycles too much.

 

[Glacier991]

How is the fan doing? A bad fan cluch can cause problems. You obviously know what you are doing, and so I'd investigate the condensor's heat removal. Your idea to recover a few ounces of the charge was a good one....