The air conditioning is blowing just air. Not hot but not cold.
I don't think the AC compressor is engaging. But I don't know how to tell for sure.
The belt is spinning the AC compressor but I don't know how to tell if the compressor clutch is actually engaged (the "knobs" are not spinning).
There is a plug with two wires which is mounted on the compressor.
Can I jump 12V to one of those two wires to see if the clutch engages? Will it hurt the ECU?
I'm no mechanic but I'd suspect no/low refrigerant first. Do A/C systems still have a sight glass to check its level like they did back in the day?
Won't hurt the ECU as long as you pull the connector off and only jumper to the correct wires. One is ground and one gets power, most however have the ground connected so that the engine is also part of the ground side. Hook power to the ground side and you will have an issue.
However as stated in the other comment, the more likely issue is low refrigerant. If you want more info including wiring diagrams and testing methods might I suggest 2CarPros.com. Enter in as much information as you can about the vehicle.
You could probably do that, but it would be easier to just attach a meter and see if there is 12V on the thing to engage the clutch.
When the clutch engages, the effect is very clear when the hood is up. The ka-chunk and then the change in running sound is very distinctive.
Note that if the system pressures are not right, the safety switches needed to allow the clutch to engage may be open.
--scott
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