Auto Air Conditioning & Heater Repair: 1994 Ford Aerostar Van, ford aerostar van, r 134a

Question
I am trying to help my neighbor with his air conditioner.  He evidently had a leak and added refidgerant to the system, but did not put in enough.  When I put on the service manifold there was just enough pressure to move the lo pressure guage off of zero.

I started by looking at the capacity: 3.33 pounds of refrigerant.  This would be 53 ounces.  I put a can of R-134a with fluorescein in first (2 oz.) followed by 4 12-ounces cans (now a total of 40 ounces).

The ambient temperature is 84 degrees.  I could get the rear cooling unit down to about 75 degrees and the front vents were about equal to ambient temperature.

Lo pressure and hi pressure readings on the guage were always the same.  They would read about 60 psi with the compressor turning and about 120 psi when off.

I do not understand how the rear unit could work at all if lo=hi pressure.  Any ideas on what could be wrong?

Answer
make sure that the high side fitting is the one on the discharge line just behind the radiator on the left side    engine size makes adiff   but some times its tempting to hook the high side to an actual lo side small service port on those that are near the accumulator drier tank on the left side that is easeir to acsess  it may be a weak compressor w/ 60 psi low side  but needs a fullcharge to determine