I just added a can of r-12 to my 93 6.5 and it sucked it all up, the can got frigid but the system seems less than what it was. It ran pretty good for no service ever, 316,000 miles. I'm not sure but the line coming out of the accumulator may be getting hot. The small line going from the condenser to the evaporator that was always very cold also may be hot now. But I felt these lines after driving with the a/c off for a few miles. I turned it off because I thought I was hearing noises coming from the evaporator area.
I was advised that it was low, worked well on cloudy days, but it seems worse now. Can anybody help me??
here are some things i've collected, may be of use, may not. tried to keep only the R12 stuff. some is old and from posters that have already replied.
1. PAG oil is used in R134a systems, same oil in any component, added to each component replaced. manual states total 8.7 oz
in system and if replacing evaporator, add 1 oz directly in evaporator.
2. must be flushed to clean out.
3. need set of gauges hooked up to high AND low side to draw vacuum. only time high side opened. draw vacuum and leave for 30 min.
vacuum lowers pressure, boils out moisture in system.
4. After vacuum drawn and held, high side valve closed, refrigerant added through low side (near the accumulator). system holds 2 lbs.
If high side valve opened at the wrong time, the refrigerant can might become hand grenade.
disconnect hoses from dryer, run flush through, include evaporator/condenser, not compressor, run shop air through to blow out
remaining flush, replace accumulator/dryer, close up system, vacuum.
Rev the engine up and what do the pressures do? 70 PSI is 70 degrees. This is a high low side condition. Maybe the compressor is bad, but the bigger question is why? Usually they knock or leak.
Do the gauges flutter? Anything but a rock solid steady reading is flutter. This would indicate a failed valve or debris in a valve cutting compressor capacity and leaving you with a high low side.
Air in the system can also do what you have. (But not flutter.)
The dual air systems as a rule should never have the rear fan speed set below medium with the AC on due to possible expansion valve failure and wiping out the compressor over time. Not that these units were that reliable to begin with.
Some info on the dual system design although the TSB may or may not apply.
http://www.thetruckstop.us/forum/sho...alve-(TXV)
Should the compressor be bad:
Replace it.
Flush the system.
Replace the orface tube.
Replace the accumulator.
Replace the expansion valve. (a PIA, but trust me it needs it.)
Possibly install a liquid line filter depending on the amount of debris in the system.
Consider replacing the condenser as they can't be flushed very well. Again depending on how much metal is in the system.
Add the correct amount of oil.
Pull a hard vac on the system.
Add refrigerant by weight. 4.0 lbs for 1995 - your year may vary.
The only way to get the correct charge in the system is to pull a vacuum and charge it by weight. Too much charge by the guess the amount can blow stuff up or just not cool really well. Too little and the compressor starves for oil, puts a bunch of metal trash in the system and then locks up. lots of folks add just enough R134a to cool well and stop. they then have the compressor start knocking on them and have a real mess to fix. The system leaking down also causes this failure. So does a stuck open TXV destroy a compressor in this system.
In other words just adding freon is a waste of your money and can cause trouble. Have it sucked down and charged properly.
