96 960: air conditioning not working correctly

[CIK7]

As you can see I remembered to put 96 960 instead of 98 XC I'm having an issue with the AC. The refrigerant is full and has almost 55psi, suppose to have only 45psi. In the service records, it shows that the AC drier unit was replaced. And it's shiny brand new. So first, it doesn't cool well. On max speed, 60°F setting, face only, its at minimum 71°F. The controllers inside dash don't switch all the way to face when set on face. How do I solve the cooling issue and do I need to take off top of dashboard to replace the controllers? Blower motor works well it seems.

[jimmy57]

The doors on that system, except the blend door (temp door) are vacuum operated. The vacuum line goes from down on side of intake manifold below throttle to over where a/c lines enter firewall in front of passenger. Make sure the hard lines and the rubber end elbows are not cracked open or obstructed internally. The recirculation vacuum servo over on far right under dash by blower can have a broken diaphragm and leak the vaccum and the floor/defrost on the side of heat-air case above and to the right of accel pedal under dash is the other leaker. You can remove the yellow hose on that that diaphragm (it has two hoses and the yellow is inboard one) and plug it. That will prevent you from having full floor air as it will only go to the mid position that gives defrost and floor without that hose on and the diaphragm working properly.
Next: to check a/c function once air distribution is dealt with you need to get engine speed to 1200-1500 using a stick between lower seat cushion front edge and the accel pedal. With the engine running at that speed the a/c compressor has pumping capacity to give you gauge readings that are valid. Once system is on with blower at one speed less than full speed and car windows up, doors closed, you then check low side pressure. 45 would be the highest and that would be 100+ degrees and it is way over 100 inside car. The pressures in green on that charge kits are right for engine idle speed (sort of) and that is not how it should be checked to get a close to correct charge. With the engine speed set and the system has run for a few with middle speed blower you should have 30-35. If you turn the blower to lowest speed and car has cooled inside then the low side on that car should drop to lower 20s and then the compressor will cycle off and pressure will rise over 6-12 seconds (less time to rise when temp outside is hotter) to mid 40s and the compressor comes back on. Rapid cycling indicates low charge on that car. There are different regulating systems used on different cars and that one uses a fixed orifice and cycles the compressor off when the pressure gets to a value indicating it is below freeze temp (assuming the charge is pretty close to correct). If the charge is low it has so little refrigerant that the low side pressure drops due to compressor suction and not due to temp. Once the compressor goes off and suction stops it goes back to 40s quickly and compressor comes right back on. If overcharged the low side pressure will not fall to lower 20s and cycle off when lowest fan is selected with a cooled interior.
The low side pressure is based on heat being removed. Higher in-car temp= higher pressure, higher blower=higher pressure, low in-car temp=lower pressure, low blower speed=lower pressure. All of this with engine speed elevated so the compressor is effective. Hybrids use electric compressors and engine speed has nothing to do with compressor. Cars with expansion valves and not orifice system will have more stable pressures but elevated engine speed is still important. Newer cars can have variable compressors and engine has little to do with getting valid system performance but elevating engine speed will get more alternator capacity and thus faster radiator/condenser cooling fan and that contributes to stable, reliable pressures for diagnosing.

[CIK7]

The doors on that system, except the blend door (temp door) are vacuum operated. The vacuum line goes from down on side of intake manifold below throttle to over where a/c lines enter firewall in front of passenger. Make sure the hard lines and the rubber end elbows are not cracked open or obstructed internally. The recirculation vacuum servo over on far right under dash by blower can have a broken diaphragm and leak the vaccum and the floor/defrost on the side of heat-air case above and to the right of accel pedal under dash is the other leaker. You can remove the yellow hose on that that diaphragm (it has two hoses and the yellow is inboard one) and plug it. That will prevent you from having full floor air as it will only go to the mid position that gives defrost and floor without that hose on and the diaphragm working properly.
Next: to check a/c function once air distribution is dealt with you need to get engine speed to 1200-1500 using a stick between lower seat cushion front edge and the accel pedal. With the engine running at that speed the a/c compressor has pumping capacity to give you gauge readings that are valid. Once system is on with blower at one speed less than full speed and car windows up, doors closed, you then check low side pressure. 45 would be the highest and that would be 100+ degrees and it is way over 100 inside car. The pressures in green on that charge kits are right for engine idle speed (sort of) and that is not how it should be checked to get a close to correct charge. With the engine speed set and the system has run for a few with middle speed blower you should have 30-35. If you turn the blower to lowest speed and car has cooled inside then the low side on that car should drop to lower 20s and then the compressor will cycle off and pressure will rise over 6-12 seconds (less time to rise when temp outside is hotter) to mid 40s and the compressor comes back on. Rapid cycling indicates low charge on that car. There are different regulating systems used on different cars and that one uses a fixed orifice and cycles the compressor off when the pressure gets to a value indicating it is below freeze temp (assuming the charge is pretty close to correct). If the charge is low it has so little refrigerant that the low side pressure drops due to compressor suction and not due to temp. Once the compressor goes off and suction stops it goes back to 40s quickly and compressor comes right back on. If overcharged the low side pressure will not fall to lower 20s and cycle off when lowest fan is selected with a cooled interior.
The low side pressure is based on heat being removed. Higher in-car temp= higher pressure, higher blower=higher pressure, low in-car temp=lower pressure, low blower speed=lower pressure. All of this with engine speed elevated so the compressor is effective. Hybrids use electric compressors and engine speed has nothing to do with compressor. Cars with expansion valves and not orifice system will have more stable pressures but elevated engine speed is still important. Newer cars can have variable compressors and engine has little to do with getting valid system performance but elevating engine speed will get more alternator capacity and thus faster radiator/condenser cooling fan and that contributes to stable, reliable pressures for diagnosing.

That's a lot of info to process. Could the orifice tube be plugged? Where on 960 would I find it? I have an orifice tube for 98 XC. Will it work on 960?