2nd Gen Non-Engine/Transmission A/c ?

[ceastmen]

What pressure should I see on the High Pressure side of the A/C?

Right now I've got between 50-60psi on the High side, the Low Pressure side is about 20-25psi.

Thanks in advance,

Chuck E.

 

[B.G. Smith]

I would say you are either out of refrigerant or in the middle of a cold spell. The vapor pressure of 134 is about 63psi at 60 deg. F. Here is some info from a FSM for 99. With outside temp of 90 deg. suction pressure should be50-60 psi, discharge pressure 215-270psi. This is with the engine running at 1000 rpm, AC in recirculatoin mode, fan speed on high. The center vent outlet temp should be 60-70 deg. Hope this helps. bg

 

[rattle trap]

Is your compressor even spinning? IIRC the low psi switch doesnt contact until 27psi.



FWIW, I measured my vent temps with a infrared thermal gun. I only did this after becoming suspicious when my hands started going numb from the cold steering wheel.



Previously during a rather humid spell after running the a/c for extended length of time, I actually froze the outside of the evaporator. Not the inside as in low psi and/or water in the lines, but the outside. The humidity froze to the evaporator blocking off all air flow. Thought a vent hose fell off because no more air was coming out the vents. Turned the heater on for a minute or 2, it thawed out and continued to work fine.



So i knew air temps down there were well below freezing, but wondered what vent temps were. A few days ago I had the opportunity to check. Ambiant Air ~81* with high humidity. Vent air from drivers side ~24*



According to the FSM, both of your pressures are low. Low/Low indicates one of the following:

low refrigerant

blocked accumulator

blocked evaporator

faulty compressor

 

[Bob4x4]

Here you go



group. Performance Temperature and Pressure

Ambient Temperature 21° C(70° F) 27° C(80° F) 32° C(90° F) 38° C(100° F) 43° C(110° F) 49° C(120° F)

Center Panel OutletDischarge Air Temperature 5 to 7° C(40 to 45° F) 13 to 16° C(55 to 60° F) 16 to 21° C(60 to 70° F) 21 to 24° C(70 to 75° F) 27 to 29° C(80 to 85° F) 29 to 32° C(85 to 90° F)

*Suction Pressure (Low Side) 241 to 276 kPa(35 to 40 psi) 276 to 345 kPa(40 to 50 psi) 345 to 414 kPa(50 to 60 psi) 414 to 483 kPa(60 to 70 psi) 483 to 552 kPa(70 to 80 psi) 552 to 586 kPa(85 to 90 psi)

*Discharge Pressure (High Side) 931 to 1000 kPa(135 to 145 psi) 1207 to 1482 kPa(175 to 215 psi) 1482 to 1862 kPa(215 to 270 psi) 1862 to 2275 kPa(270 to 330 psi) 2344 to 2551 kPa(340 to 370 psi) 2758 to 2965 kPa(400 to 430 psi)

*Note: If pressures are lower than shown, but center panel outlet discharge air temperatures are OK, then the A/C system is OK.

 

[Crash&Burn]

Here you go



group. Performance Temperature and Pressure

Ambient Temperature 21° C(70° F) 27° C(80° F) 32° C(90° F) 38° C(100° F) 43° C(110° F) 49° C(120° F)

Center Panel OutletDischarge Air Temperature 5 to 7° C(40 to 45° F) 13 to 16° C(55 to 60° F) 16 to 21° C(60 to 70° F) 21 to 24° C(70 to 75° F) 27 to 29° C(80 to 85° F) 29 to 32° C(85 to 90° F)

*Suction Pressure (Low Side) 241 to 276 kPa(35 to 40 psi) 276 to 345 kPa(40 to 50 psi) 345 to 414 kPa(50 to 60 psi) 414 to 483 kPa(60 to 70 psi) 483 to 552 kPa(70 to 80 psi) 552 to 586 kPa(85 to 90 psi)

*Discharge Pressure (High Side) 931 to 1000 kPa(135 to 145 psi) 1207 to 1482 kPa(175 to 215 psi) 1482 to 1862 kPa(215 to 270 psi) 1862 to 2275 kPa(270 to 330 psi) 2344 to 2551 kPa(340 to 370 psi) 2758 to 2965 kPa(400 to 430 psi)

*Note: If pressures are lower than shown, but center panel outlet discharge air temperatures are OK, then the A/C system is OK.

This chart is good, but doesn't mention what "MODE" the raditor fan clutch is in... ... if the clutch disengages (stops pulling) the head (high) pressure will shoot as much as a 100psi, but will return as soon as the fan pulls again. .

 

[B.G. Smith]

This chart is good, but doesn't mention what "MODE" the raditor fan clutch is in... ... if the clutch disengages (stops pulling) the head (high) pressure will shoot as much as a 100psi, but will return as soon as the fan pulls again. .

That chart is from the FSM and is supposed to be a test of the system with the engine running at 1000 rpm, the AC in max mode with the fan on high. If you notice, the outside air temp is listesd at 70 deg. F. If the fan clutcxh is in normal working order and the radiator is not completely plugged you would not ever hear or see it engage under these conditions unless you threw a blanket over the radiator. bg

 

[Crash&Burn]

That chart is from the FSM and is supposed to be a test of the system with the engine running at 1000 rpm, the AC in max mode with the fan on high. If you notice, the outside air temp is listesd at 70 deg. F. If the fan clutcxh is in normal working order and the radiator is not completely plugged you would not ever hear or see it engage under these conditions unless you threw a blanket over the radiator. bg

The way I read it, it's has readings for 70, 80, 90, 100, 110, 120 degrees outside temp.....

 

[B.G. Smith]

The way I read it, it's has readings for 70, 80, 90, 100, 110, 120 degrees outside temp.....

My mistake, you are correct. With some of the higher ambient temps the fan clutch might engage. bg

 

[BDaugherty]

Charging a system by pressure alone is not an accurate way of doing it. Your high side pressure is low. Somewhere between 190-230 psi would be normal for the high side at idle with ambient temps around 75-80 deg. The best thing to do is really to start from a vacuum and charge in such a way that you know how much refrigerant you have added. The second best method is to stick a temp gauge in one of the vents and charge slowly. When the vent air temp stops going down, stop charging. Remember that high and low side pressures will vary greatly depending on ambient air temps, engine speed, air flow through the condenser, relative humidity, etc.