I have a 1990 Ford Ranger xlt with around 112,000 miles on it. I just recently replaced the compressor and evaporator because the compressor had a leak and the evaporator was all rusted. I put PAG oil in it and I made sure to fill it up with the right amount of refrigerant. I know the compressor coming on then off is usually a low sign of freeon but it baffles me how it could lose upwards of 20oz of freeon in just the weekend. I woke up this morning and pushed the button that turns the compressor on and off and put it in off then I turned my heat up and put it on defrost. When I came back out after about 10 minutes I could hear the compressor clicking on then clicking off on my way walking up to the truck. Just yesterday it was in the mid 80s and my A/c was getting to about 50°f. I’m looking for other opinions because im praying it’s not leaking after I spent around 5 hours replacing it.
A 1990 model I believe would have been originally equipped with R12a refrigerant. Presumably yours was converted to R134a?
How frequently is the compressor cycling? Depending on the design of the AC system some cycling may be normal. (For example, my 1999 Jeep Cherokee shop manual specifies that compressor cycling is dependent on ambient temperature and is considered to be too rapid if it reaches more than 10 times per minute.)
Hook up your gauge set and check pressures. (A 1990 model most likely does not have a variable-displacement compressor so you can judge the charge level by pressures pretty well.) Check your system pressures against an R134a pressure chart. They don't have to be exact but should be fairly close. Also, if refrigerant level is low typically the low side will quickly go too deep into suction, dropping pressure below the level of the safety cutoff switch (usually about 20 psi) and turning the compressor off until pressure rises above that level.
https://www.warnockauto.com/r134a-pressure-chart/
At 4:10 Scotty says when the system is rusted, it's pretty much shot
https://youtu.be/2Bj22gFCq7A?si=DNowBJVNpFotJ8nX
