I have a 91 Ranger that the A/C was working great in but all of a sudden it stoped working even the fann. I turned it of and back on and it started again but then just stopped for good I can get the fan to work sometime, but no cold air. anyone have a sugestion on what it might be?

 

Generally there is a pressure switch that disables the compressor when the refrigerant is low. Given the age, that would be R12 in that system unless it's been upgraded to a 134A system. It could be an o-ring leak, leak in compressor, accumulator, condenser or evaporator. Expect the cost of the R12 to be quite expensive. If it's a compressor (given the age) I'd would recommend converting it to a 134A system.

 

If it was working well, and stopped suddenly, with the fan stopping too, it sounds more like an electrical problem than a refrigerant problem. If you have a standard system, the fan switch has 4 positions. Power is fed through the switch to a resistor 'pack' that is then connected to the fan motor. The fan switch ALSO is in the A/C clutch power path. If the fan is off, the a/c clutch won't get power. That is if you have a push-button on the control, which is released when the blower switch is in the 'off' position. Can't say for sure about the other styles, but it makes sense they'd disengage the clutch when the fan was off. You could have a worn out blower motor at this age.
Check for consistent power to the blower motor, and then work back from the clutch checking to see if there is power and when it is interrupted. There are several switches. low pressure, high pressure and wide open throttle, all of which can cut clutch power in addition to the switch, fuse and source. In addition, there is a 'shoe' or brush that transfers power to the rotating clutch from the compressor body. You should have clutch power with the system in A/C mode, the fan on, and the ignition on.
tom