I suggest you get help from someone that knows about a/c. There are many possible causes for an a/c to stop working.
What do you mean when you say "I checked both the low pressure pipe and the R-134a have pressed oil"
Are u sure the Escort 94 has R134 as refrigerant? Was it converted from R12 to R134?
If the problem is just that the system is low in refrigerant:
If the system is low in refrigerant? Is the system empty? If the system is empty you need to evacuate it using a vacuum pump,until the low pressure gauge drops to 29.92 in Hg or the proper value according to altitute with respect to sea-level. Moisture (air) in the system will clog the expansion valve when it cools down. Moisture will also attack the compressor oil.
If the system is low in refrigerant, the compressor may not run because of the cut-off pressure switch. You need to put refrigerant in the system until the switch closes (normally between 20-30 psi).
To charge the system, connect the hose attached to the refrigerant can to the low pressure refrigerant line. The best way to put refrigerant in the system is with the can upside down, opening the valve just a little bit. If you open the valve too much there is a risk of damage to the compressor.
You should put refrigerant in the system until the sightglass (if equipped) shows clear, without bubbles. If there is not sight glass, the best way is to put the approximate amount (by weight or number of cans) suggested by the manufacturer. If this info is not available, then you can put refrigerant until the low pressure side has a pressure between 16 psi (at T amb=68F) to 38 psi (at T amb=104F).
Again, I suggest you look for someone that knows about A/Cs.
Good luck!
Leo wrote: