I have an 86 which has the same type AC that you have.

Check the coolant level first just to get it running.

If you want to improve how it works try this,

Most R134 conversions have too much oil, too much coolant, and are still restricted with gunk. What you get is a marginal system and not much cool. Have your pro drain any remaining coolant out of the car.

A complete clean out with cleaner along with a new dryer and expansion valve and a bottle of Pag 40 is the place I would start. If you have the money and time, the other component to change is the condenser. You can get decent results using the old one if you do not have any leaks.

Remove the dryer and expansion valve and pull and drain the compressor. Pour Pag oil down in the compressor and drain it really well. Make sure the fittings are nice and snug on the compressor. Now flush out all the lines starting with the two lines inside the car. You want to flush the oil and gunk up in the lines from the inside of the car, one side of the expansion valve goes through the condenser and out to the compressor. The other line goes to the dryer. Then you clean out the line from the dryer to the compressor. That will clean out the evaporator, condenser, and all the lines. Go inside the car again and with compressed air blow the cleaner and other junk from all the lines, I suggest a mask and good ventilation. Now you fill the compressor with new clean PAG 40 oil, and start reassembly of the of the lines. Lube all the new orings with PAG before you slip them into the fittings and tighten. Install the expansion valve next inside the car. You want to wrap the lines inside the car with a good insulator. The last thing installed is the dryer, move the low pressure switch, pour 1 oz of Pag (Subtract that from the compressor amount) in the dryer and install the two lines with Pag 40 lubed o-rings.

You will a set of gauges and a short wire with a couple of spade lugs, four cans of R134 and a loaner compressor from one of the chain stores.

Connect the high and low side up and jumper the low pressure switch over on the dryer. Hook up your compressor to the center of the gauges and start up the pump, slowly open both the high and low side of the compressor. After about 15 min close off the red or high side valve and continue pulling the vacuum on the low side. Run it at least an hour after the pressure reaches zero. Turn off the valve on low side and and turn off the compressor. You should have a vacuum after 30 min after you close the valves and turn off the compressor.

If you know you had a tight system before you opened it up and no compressor you can do the red neck vacuum. Jumper the low pressure switch and start the car. When the compressor starts growling you are ready to fill. That is also how you start doing the fill on a vacuumed system. Connect a can of R134 to the yellow line and and spike the can, and slowly open the valve. Slowly open the blue valve and the can should start getting cold. Keep your pressure below 50 psi during your fill. When the can goes warm close the blue valve and put on another can. About half way into can 2 you should start feeling the system start to cool, stay the course and keep the pressure under 50 psi. When you have installed the third can of coolant you should have cold air out of the vents. To do the final fill you want nice hot weather and do not over fill the system. You need to add just two more oz of coolant and that is hard to measure. So read your pressures and go for a drive, before you add a whole lot more. At 95 degrees you should have pressures in the low 40's on the low and over 220 on the high. In the upper 80s' 35 to 37 and pressures close to 200. An overcharged system does not work worth a flip so drive and add as needed is how I do it.

You should have air in the low 40's coming out of the vents at highway speeds. My R134 system runs better than the R12 ever did, I think the expansion valve has to be part of the issue. Just by flushing out the old oil and installing an new expansion valve when replacing the compressor resulted in a well running system.

I had a quote for $945 plus tax to fix Inga from a decent shop here in town. For a $50 PUP compressor, a can of Pag, a $7 set of orings,$20 in coolant, $20 for a dryer, and $20 for an expansion valve and I had a working AC. Did take me all weekend to do the job. But for less than $130 in parts Inga was goo to go.

After getting the AC working did add in a pusher fan, belly pan, tropical fan clutch (AKA Swamp Cooler), and some Reflectix in the roof. 15 minutes after starting her up and heading home the fan is on 3 and the knob is just above the blue. Closer to home the fan is on 2 and slow speed or not speed still have cold air coming out of the vents.

Regards,

Paul