My 91 240 sedan 228K miles has been converted to R134 about 120K ago.
I hasn't been cooling like it used to, in fact it is just hot on days over 80 degrees, but on cooler days (under 80) cools pretty well. I notice the compressor doesn't kick on as often as it used to. Is there a switch or sensor that may have fouled? Or: Is this a case of low coolant? Should I buy some coolant and fill it up or is this a job for a certified technician only? Should I go to a Volvo person Non dealer or any old car care shop that does A/C work?

I replaced the fan motor about a year ago with a used one, and it started squealing again.
I don't want to replace it again, unless I know the A/C is OK, and don't want to spend too much finding out.

I live in Houston and want to get this cured before summer arrives. This car is mostly used by my High school senior daughter, and I don't know how she dealt with the heat and squeal, but I guess any car is better than walking. . .