A/C blows warm air

If the compressor clutch engages and turns the compressor, but the A/C still does not blow cold air, the system is probably low on refrigerant and needs to be recharged

This guide can help us fix it:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Please run down this guide and report back.

To check for a vacuum leak, it's usually easier to start at the actuator itself if you can get to it. If you can, unplug the vac. Line from it. With the vehicle running, move the switch back and forth from hot to cold and see if there's any vacuum at the line you just unplugged. Keep in mind that it will be a very small amount of vacuum so it's not going to suck your finger to it real hard like a brake booster line. If there is vacuum there, then the actuator is most likely bad. The diaphram inside them can go bad and not move the arm when vac. Is applied. If there's NOT any vac. Move to the control head in the dash. You can remove it without tearing a lot of the dash apart. Unplug the vacuum connector at the back of it. Again, with the engine running, see if there is ANY vacuum on one of the lines. If not, go under the hood. Look for a black vacuum line going through the firewall into the passenger compartment. It will come from the engine or maybe even the line going to the brake booster. There will be a small black "check valve" inline. Check that line where it originates and see if there's vacuum there.

You can have the AC on and, at the same time, have the temp. Set to HOT. So, YES, you can have them both on at the same time. In your first post, you mentioned that the AC was cycling too much. If it's cycling pretty fast, that usually means that the system is low on freon. The low pressure switch is turning it off when it gets to a low pressure condition. OR. The HIGH side could be 'pegging' out and the same thing could happen. If the orfice is stopped up, when the compressor engages, the high side will increase pressure quickly and the HIGH pressure switch will cut it off. You'll need to connect a set of AC guages to varify.
I just read up on this system. The temp. Is controlled by an electric motor. There are 3 vacuum actuators but NONE of them control the temperature. They control the floor/panel, fresh air/recirc, and panel/defrost. The blend door(temp.) Is controlled by an electric actuator.
The code 02 you mentioned is for EATC connector and blend door actuator. I think we're on to something here. It's telling you that there is a problem with the actuator and that's why you can only get heat out of the vents. Go directly to the actuator. I'm pretty confident that you'll solve your problem by replacing it. First make sure it's plugged in.
You can test it if you like. Find the wires going to the actuator. (Purple and Brown/light green) Apply battery voltage to one wire at a time. The actuator should move in one direction. Change wires and the actuator should move in the opposite direction. If it doesn't, replace it. If it does, repost and let me know and I'll walk you through further diagnosing.

Turn A/C on, open the hood, is the compressor cluych engaged? If not you may be low on R-134a. If the A/C compressor is working, Run the self diagnostic test on it by turning the key to on, then press off and floor at the same time, then within 2 secs, press auto, If there is a problem a trouble code will appear on the display. To exit self test, press the BLUE, cooler button this also retains error codes, To erase code and exit, press defrost, choose one of these before you power down the system. Test with engine at 120 degrees or more, and cabine between 40-90 degrees. Post any codes recorded here and I let you know what's defective.

They will be under the dash. Maybe behind the glove box, or on the bottom of the evap case on the passenger side. It may be easier to pull the control head out and find the wires there. Don't disconnect anything. Just find the wire, pierce the insulation and apply voltage and see if the actuator moves. I use a "POWER PROBE" but if you don't have one, you'll have to make a jumper connected to battery voltage. Be careful not to arc the wire to ground. In fact, if you have to build a jumper, it would be best to include an 'inline' fuse in it just in case you touch it to ground. We don't want a melt down.

Did you convert, before you had problems. And it worked fine?

Do your A/C gauges show you are at or near correct pressure?

Does the inner center portion of your compressor turn, when A/C is turned on?

Have you looked in owners manual or in the Fuse Box tops for A/C related fuses?

The WHOLE PICTURE, sometimes helps, on this end.

The Medic

Hi
Suspect fault in vacuum select valve see diagram

if it does not direct vacuum to correct servo then mode selection is not possible. Do you hear like a hissing sound sometimes from control unit? Need to remove and inspect unit can be replaced no need to replace entire controler.
Let me know
Thanks for donate

Unfortunatly in 92 USA went to R-134a and banned the use of R12! Your 91 unless already converted is R12! Take it to a knowledgable A/C shop.I've seen a guy blow 3 fingers off his hand hooking up an R12 can the wrong way!

Your probably low on refrigerant. The compressor can kick on and off if low on refrigerant. R12 refrigerant may be hard to come by and expensive.

Usually if the compressor is kicking on and off, the refrigerant is low. If that isn't the case, might be issue with ac pressure switch? Any applicable trouble codes? Also, check directional doors under the dash.