Most of the system oil sits in your Accumulator/Drier. Its always best to remove the accumulator and drian the oil that was in there and replace the same amount of oil that came out of there. Too much oil is no good. Most times the accumulator is cheap enough just to replace. The system should be flushed with a/c system flush solvent to get all of the old oil out of it.
Your van has one orifice tube that is located in the front evaporator core inlet tube. I'm not 100% sure but I think that ford uses an expansion valve instead on the rear. I know that GM only uses one orifice for their rear a/c systems on their yukon. so having just one on a dual system is normal. With the use of only one orifice tube the rear would work better because the orifice tube is located at the front evaporator core inlet tube, if it is dirty it will restrict flow going to your front evaporator.
As for charging the system, This is to give you an idea of the charge pressure needed on the low side.
Ambient Temp vs PSI
65F 25-35PSI
70F 35-40PSI
75F 35-45PSI
80F 40-50PSI
85-90F 45-55PSI
95-110F 50-55PSI
Do not ever charge.
Hope this helps.
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Originally Posted by Old Nuke ET
Nope - I did not drain the old oil - so two questions - where is the appropriate drain point for the system oil (besides just picking a low point on the condenser) and I have pretty much traced out all the lines and have yet to figure out where these orifice tubes are located. Is it reasonable to assume that both the front and rear lines would have individual orifice tubes even though they use the same compressor? If there is only one for the entire system then why would the rear be good and cold but the front be so-so?
Also - and I'm not giving in to pride here - but I am not THAT confused about pressure / temperature relationships. The "Old Nuke ET" name comes from 9 years operating a reactor on a sub...
Thanks for any help you can give
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