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I looked in search, but did not see this particular problem. Have just bought another 1990 Bronco EB, 351W, full size. The previous owner said he had the a/c system "serviced" last summer,for the second time, but still had no cold air, for the second time. This system was converted to R-134 in 2004.The system was separated, the lines flushed, the condenser flushed and blown out. The evap. core was flushed and blown out. The accumulator was replaced. The cycling switch was replaced. A new orifice tube and filter was installed. The system was pulled to a vacuum (about 26"), and left to rest for about 45 min., and held a good vacuum. R-134 freon was being installed, but the system would only take about 1-1/2 cans or less. The low side reading was about 80-100#, and the high side was about 35-40#. Outside air temp when this was done was about 85 degrees, high humidity (rain on the horizon).The high side line (replaced w/ a line containing the R-134 port) just before entering the condenser is extremely hot to the touch (the gauge fitting is the same) (Hot enough to blister a finger!). The line out of the condenser going to the orifice filter and evap. core is luke warm. The air coming from the vent only gets cool when the engine is run at about 2000 rpm +, or driving down the road at 55-60 + mph. The vent temp is probably 10 degrees less than the outside air temp. The orifice filter that was taken from the vehicle was melted because someone tried to heat it to get it out, and broke it into a number of pieces (Don't know what was in/on that filter). When the system was disassembled for the second time, there was a lot of oil on the filter, but no particles or residue. The oil was blackish looking. The previous owner said that the tech added about 2 oz. of R-134 oil when it was "serviced". Could it be a compressor problem? Could the orifice filter be in backwards? I'm thinking that the filter screen end is supposed to be nearest to the evap. core (pointed downward in the orifice tube), right? Any ideas or suggestions are appreciated. Thanks.
 

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i got lost somewhere in that huge paragraph..
but if the low side had way more pressure than the high side, that would indicate to me that there is a plug in the system somewhere between the accumulator (where you filled/measured the low side) and the spot at which you measured the high side..

it seems unlikely to me that a compressor would go bad in such a way that it would act as a plug (and still turn normally) so i would have to think the problem is in the filter after the compressor (before the high side pressure test point)

maybe try taking the lines off, make sure you can blow through them (to be sure they are clear) and also check that filter.
if the oil was black, it could have "black death" so you may need to replace everything. i *think* black death can come from mixing incompatible oils.
 

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The pressure readings indicate faulty reed valves in the compressor according to my A/C troubleshooting tree, do you have a set of gauges? At @ 85 ambient your pressures should be @ (low) 45-55 psi and (high) 225-250 psi. My A/C unit took @4 cans of refrigerant. If you have the "Black Death" the compressor maybe toast.

It is possible to put the orifice in backwards, but the detail that you gave, or was given to you, indicates a fairly good understanding of the system. But it can be done given the various orifice tube mods that can show up on a 20 year old vehicle. Goog Luck.
 
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