there are different types of AC units witch makes it difficult to answer your question, but I think the kiss theory works here. Ether your fan is not working or your evaporator coil is iced over. there are several reasons for the coil to be iced over. the main one is it needs to be cleaned dirt and dust will restrict the air flow and cause it to ice over.
The AC isn't working.
Is the AC condenser in your system blowing cold air?
i know the AC in my ZX2 stopped blowing because of a loose wire
There may be a stuck vent door or an issue with the heater blower control head.
Your AC may keep blowing a fuse due to an electrical overload, a short circuit, or a faulty component within the system. It is important to have a professional inspect and repair the AC to prevent further damage.
Your engine is hot.
Could be no Freon in it.
a long time
If your ac is making noises or is blowing hot air instead of cold
If a Jeep Grand Cherokee's air conditioner is not blowing any air it could mean that the blower motor has went out. Also the AC controls could be bad.
It usually means that your system has developed a leak. Your AC system is charged with freon gas. If a certain amount leaks out, a safety device prevents the AC compressor from starting. Without the compressor, no cold air.
Your AC might be blowing out of dash vents on the windscreen as you might have turned the knob to that particular mode. It is also possible that the vent mechanism might be out of order or broken.