What type of freon is used in a 1989 3.o v6 toyota pick up

SOURCE: ac not working, blows hot air only. Recharged

Check the evaporator coil by sniffing the vents,floor is best, with your tester.

SOURCE: the ac only blows warm air, have recharged it with freon but it only cools minutes before blowing warm again, could find no leaks

There are special cans of R-134A with dye in them for detecting leaks. Most leaks occur around the fittings near the compressor. Recharge the system with the leak detector can or R-134A. There are also cans of R-134A with an additive to stop leaks. I would use these products to either detect your leak or to stop it. Best of luck.
Greg

SOURCE: 97 Olds Aurora AC blowing warm air a day after recharging system

Several- The system should hold freon for years without leaking. There are pressure switches and they cut off the compressor with an undercharge and an overcharge. You need guages to measure the charge. There are testers the A/C shops have called "sniffers" which can detect a leak. If you have no leak then you need a technician to add or remove freon to get the concentration right. Or you need guages.

SOURCE: How can I do my own AC recharge

Assuming you do not have a leak preventing a recharge, here are some basic steps on recharging:
http://www.aa1car.com/library/ac_recharging.htm

R134a can be purchased at any auto parts store..

SOURCE: need to recharge ac in 1995 chevrolet blazer. Not

1995 should have 134A. Look on the compressor and in the middle of it will be a sticker that says 134a or r12. If it is r12, you must retrofit it in order to charge it yourself.