On the Surf/4 runner ther are 4 posible causes for this to happen all but one cheap and easy to fix.
1> High Pressure swich faulty. Look inside engin bay for small gas cylender (follow small pipe from condensor in front on goes to compressor other to the tank) on the tank you will find a smal (normaly black) sensor with two wires. If the fan condensor fan is working is workink brige out the switch you will hear a click fron the pully if it energises. If this is the problem simply unscrew the sensor and get a new one from a car ac repair shop. screw back in and replace wireing It does not mater wich wire goes where. A warning thoug do not drive and use the ac with the wire bridged. the swiych cost about $30 or you can suport toyota and pay $80 it comes from the same factory so no one will know.
2> Low pressure swich failure.not all have this but later models have had some clever upgrades saving you lots of money in the long run. Follow big pipe from compressor and the same prosedure as before.
1 and 2 are both safteys one for over pressure and one out of gas.
3>Check the puly solinoid. next to the pully on the compressor are two wires use a multimeter to find the positive and negative on the pump if you have a supply to the solinoid chances are good it had its days. Once again go to a ac repair shop AND ASK THEM TO REPLACE IT chanses of damaging the shaft seal is good when removing the bearing so Get them to quote you a price before they start. DO NOT ATEMPT THIS AT HOME 99% CHANCE OF COSTING YOU MORE at the end of the day.
4> READ THIS; System short of gas. even thoug there might still be gas in the system it might not be enough thus an lp swich a system gets damaged 123 if it runs without gas it normaly loses its oil if it loses gas thus its a safty.

Im a qualified refreigeration engineer so if you have any more questions feel free to ask.
Cheers Corne