Chrysler Repair: Town and Country Van 1996 AC High side problem, pressure transducer, frequent failure

Question
Roland,
I have be trying to fix the wifes 1996 LXI T&C van. The A/C does not always get cold. I set up guages and found the high side to rise up to 250 PSI when it is not working well and down to 75-110 psi when working. It seems the high side pressure goes up when the fan is not on and the high pressure line gets super hot. I suspect there is a problem with the fan not turing on soon enough. I tried to see if I could find a temp switch for the fan but found none. There is some sort of sensor on the high side line (looks like it may not be servicable) that dissables the clutch when I unplug it. Also the low side when working runs around 15-30 PSI is this correct? or am I incorrectly charged? I did not find the charge capacity in the owners manual This is a Town & Country LXI 1996 van with rear A/C.

Thanks so much,
Jim

Answer
Hi Jim,
A/C is not my forte. That high pressure (250) seems to be about correct, according the shop manual as does the low side number; but why 75-110 produces the best cooling is an unknown for me. The fans and the A/C clutch are both controlled by relays which are actuated by the powertrain controller. The wires from the controller to the relays control lines are light green/dark blue and dark blue/orange, respectively. There is a "pressure transducer" which is what I believed you to be describing as a sensor that is an input to the powertrain controller that is measuring the pressure at that point of the system. Another fellow with an AC problem replaced his because it was not cutting out the compressor at all (overpressurizing the system with resultant blow off of refrigerant) and when he bought the part the dealer counter-person said they had a re-design in the mid-90's for the transducer because of frequent failure. The wires to that are:dark blue, violet/white, and black/light blue. He bought a new one for a little under $100 and replaced it himself without having to remove the refrigerant from the system. But whether that is the cause of your present problem is something I can't be sure of.  I think there is an evaporator valve that may be faulty and not giving you the expansion that you need to get the coils cooled, at least that is worth considering. I have not fiddled with the hydraulics myself, and prefer to let a skilled independent shop do it unless it is pretty obviously an electrical control rather than an hydraulic issue.
Roland