I am new to the forum and would like to see if I can get some advice on charging my AC system. The clutch started slipping and I decided that the best way to go with what should be a "sterile" system would be starting from scratch with a completely new system (seemed like a good idea anyway). So I put in a new compressor, evap, condenser, and lines along with drier, added 9 oz of oil (compressor came with 7 oz and I added 2 to the accumulator) as the sticker on the frame says and I then weighed out 38 oz from 12oz cans, which I know isn't ideal. Now I have a system that is reading 50psi on the low side, 242 psi on the high side (90F day) and it never cycles. Looking in the manual, best thing I can figure is that the orifice orings are leaking. I evacuated it a second time, replaced the orifice and am getting roughly the same readings. What am I missing? Suggestions for a way forward? Thanks!


1996 F350 4WD Crew Cab
7.3L PSD

 

Are the orings still leaking?

 

I am not sure if the oring is/was leaking still. How might I troubleshoot that? Replace the evap with another? What other things could this be? I know the engine is not overheating and I don't think the new compressor is bad. It could be that I am not getting adequate flow over the condenser (how to test the fan?). I think with the suction pressure high and the high pressure normal to high and compressor constantly running that those are my most likely suspects, but could be mistaken. Thanks!

 

You didn't mention vacuuming the system, you did that, right?

 

Yes! I got it down to 30 inHg for one hour and it held the vacuum for 10 min per the Ford service manual.

 

what do you mean by "it never cycles"
50 low side and 242 high side on 90F ambient temp is about rite for pressures.
what is the temp coning out of the center vent with the van on high and control set to max AC?

 

The temp in the center vent is 61-62F on high with Max AC. If I am reading the charts in the service manual correctly, I should be seeing the low pressure cycle between 45 and 25 psi on a 90F day and high pressure cycle from 150 up to 250 psi.


Something else I noticed is that my fan clutch is almost certainly slipping so I am going to replace it and see how much that helps. Anything else to check?

 

Get proper air flow across the condensor . Proper air flow across the e vap. Then max ac, high fan, look for 35 -38 psi on the low side . 200 To 180 high side idle . Should be spot on .

 

Unfortunately after changing the fan clutch I am not much better off than before. On an 85F night and I am seeing steady 60 psi on the low side and almost 290 psi high side. 62F coming out of the center vent on high/max AC. I am confident that I have sufficient airflow over the condenser and checking the evap.

 

I'm no expert, but that sounds like you have a blockage, or partial blockage, somewhere in the system.

 

Fan shroud in place, no debris blocking radiator?

 

If all is "new " and proper air flow . No bad components ... You are over charged ..
Blend door functioning properly , heater cut off , if equipped , working ...
Pinch off your heater hoses with some vice grips wrapped with cloth . See if that changes anything . You may have a blend door , shut off issue .

 

You change the orifice tube?

 

I did. Changed the tube as part of the evap. Ended up trying two separate(identical) red orifices, both with new O-rings. No change that I could detect

 

is the compressor in fact operating? Can you see the compressor clutch spinning? If it is, and you are sure of your charge (freon amount) the next place to go to is your blend door, -and/or blend door actuator.. if your blend door is stuck, or the little plastic tab on the actuator is broken, you will have mixed air (hot/cold) coming into the cab.. also, check your coils, if they are clogged with dust you will not get good air flow over them, therefore you will not get good cooling of the air. Also, some units have a cabin filter, if your model does, it should probably get replaced as well, this will help with good air flow over the coil.