Chrysler Repair: New Yorker A/C problem, inner fender, rectangular block

Question
1988 New Yorker 130,000. The past week I have noticed my A/C will not always kick on when I turn it on. Or it will run for a few minutes then blow warm air. Today I drove to an appointment and it worked fine. Came out and it would not work. I can usually tell if the compressor comes on and it wasn't. Got onto the highway and turned it on and alas, it worked. Went to the grocery store, came out and it worked fine. I went to run another errand this afternoon and NO AC. The compressor is not kicking on. What could it be? Your help is greatly appreciated...Deborah

Answer
Hi Deborah,
The on again off again behavior suggests the problem is with the refrigerant level. There is a pressure switch which will defeat the compressor when it senses the pressure is too low. You may be able to determine visually whether that is true. Take a look under the hood on the right inner fender for a small round solid black metal container near the compressor with incoming and outgoing small diameter refrigerant lines that are attached to a rectangular block on the top of the container. Notice whether there is a small round glass window in the rectangular block or not. If there is, then we may be able to determine if the issue is low refrigerant level. Idle the engine and turn on the A/C on high and the temp on cool. Look in the sight glass to see if there is any foam or bubbles showing. If so then it is possible that the refrigerant is low. To put it to the test put a tarp or blanket in front of the car's grill and rev the engine to about 1400 rpm (this will raise the pressure in the system), and if it still shows bubbles it is definitely low on refrigerant. If you don't see any bubbles and the unit has produced cool air recently, then the problem may be due to the air handling system in the console or something else related to the refrigerant handling, but because of the way you describe it, I do expect it is just low refrigerant. If you can't find a sight glass on the small round container, then only an AC shop can determine that. The most likely reason for your problem is that the refrigerant is low, particularly if you haven't had to service it for a few years. In that case the AC shop is the place to have it done rather than the dealer because they generally charge less and know their craft. If you have not had the unit modified to use R-134 refrigerant (the envionmentally friendly chemical) it may be suggested that you do so. On a car of 17 years age, that is a tough choice to make. The R-12 refrigerant is much more expensive, but if you only have to add a little of it you might be better off to do that rather than to go to the expense of mechanically modifying the unit to use R-134 and refilling it with R-134. I would ask for two estimates for either of those choices. It may well be that the system is not leaking very significantly (or at all, if the problem has nothing to do with the refrigerant being low) so don't give up on the existing fill of R-12 unless the economics look attractive over the expected life remaining in the vehicle.
Roland