94 940 wagon question about A/c

My ac dosent work at all. What is the process to change that? Is it the new or old style ac? can it be recharged? what is generally the cost?

You have the new R134a system, being a 94' model. I would star by buying a R134a can of refrigerant that has a gauge on it. Or buy the hose and gauge by itself. In the morning when everything is cool and even measure the ambient temperature in front of the condenser, front grill of the car. Now hook the gauge coupler into the low side port by the dryer, it should have a tag saying 134a. The preassure should be:
68PSI 68F.
70PSI 69F.
72PSI 71F.
74PSI 72F.
76PSI 73F.
78PSI 75F.
80PSI 76F.
85PSI 79F.
If the preassure is a lot lower than the corresponding temperature you are low in refrigerant. You may have a leak, or just low refrigerant.
You will have a rain of posts in a bit on this matter. No panic, just yet.

Here comes the rain. There is one more thing you can do before spending money on gear. Check that the compressor works. You can do several things. With the ignition ON, engine not running, go to a little box near the strut tower driver side, uncover the one towards the front of the car, pull the terminal on the side of it and plug it into #2. Push the buttom by the led light three times: push... one sec, let go...one sec, push...one sec, that three times. The system will run a self diagnostic through several components and one will be the compressor. If the compressor is engaging you will hear a loud click two times. If it does not, desconect the diagnostic terminal and turn ignition off. Pull the pressostat plug from the dryer, big can looking thing by the firewall passenger side. Make a jumper and jump the two terminals in the plug. Run a disnostic the same way again. If not click yet, stop diagnostic, turn ignition off. Here you may have a fault between the pressostat and the compressor. Unplug the wire to the compressor, make a three feet jumper and connect the compressor directly to the + terminal on the battery. If you hear a loaud click you compressor seems to be OK and you are probably low in refrigerat or may have a faulty pressostat.