well so far in this thread we've covered everything from "black death" to low freon. Until about 1994 or 1995 most manufacturers used R-12 in auto refrigeration systems. It was determined that R-12 (a chloroflourocarbon based substance) was depleting Ozone. It's manufacture was banned post 1996, so most automakers looked for a chlorine free substitute... voila R-134a. It is still what they use.
Regardless fo the refrigerant the cycle is the same. A compressor compresses gas into a liquid, causing heating. The heated liquid runs through a condensor (think radiator) where air removes heat. The liquid is directed to an expansion valve, which allows a metered amount of refrigerant to pass and expand into a gas. That expansion causes it to cool, and it picks up heat through the "evaporator) think small radiator in the passenger compartment) where it passes back to the compressor to begin the cycle again. If you are interested it is the "latent heat of vaporization" that make this whole thing work, more or less.
Now, what can go wrong? Well, in the simplest of systems, if you do not have enough refrigerant, that'll do it, and in a lion's share of cases that IS it. Fair enough, have someone put a gauge set on it and run the system and see. Not a simple auto parts store gauge, but a refrigerant gauge set. Your comment about 143 pounds makes no sense because you should have been charging into the low side, which does NOT get that high. Also.. you cannot MIX refrigerants! If you have an R-12 system you HAVE to add R-12. R-134a needs R-134a. AVOID SUBSTITUTES!!!! DO NOT UNDER ANY CIRCUMSTANCE attempt a DIY conversion from R-12 to R-134a. Why ? They DO NOT WORK for long term and will ruin your compressor or worse. AC people refer to these as death kits.
Ok if there is an adequate charge and NO AC, then what? Now we start to get into what makes each individual system different. It could be a defective pow pressure switch preventing the compressor from running. If the clutch cycles the low pressure switch probably can be eliminated. The compressor could be burning up and have thrown off metal shavings and soot clogging the expansion valve. This is the so called black death, and not uncommon on EXplorers where the fx-10 and fx-15 compressors seemed prone to lack of lubrication failures. Although a replacement of this little plastic valve may temporarily solve the problem, it usually means a "firewall forward" rebuild. I did one on my 92 Explorer, and at my discount the parts - condensor, compressor, accumulator, receiver dryer, expansion valve and R-12 cost me nearly $600. And that was without ANY labor or parts markup.
The list of possibles goes on from there, most system dependent.
Without checking a dealer cannot tell what the problem is, and to just assume no cool air means a $2000 rebuild is stupid. Take it to a good AC shop and have them check it for you. It will be money well spent. I do AC, have the training, and see more problems arising from DIY kits than any other single source. Hope this helps.
Chris
shoulder.
