AC Compressor will not engage on 92 Explorer

My 92 Ford Explorer A/C has stopped functioning. The blower fan and the AC LED comes on but the compressor does not engage. I connected a volt meter to the signal/power leads the attaches to the compressor and do not get any reading . Additionally, have checked the 10 AMP fuse and it appears to be fine. Please Advise.

Your compressor is protected by a coolant pressure switch. If your system coolant is low, the switch will keep the compressor from engaging which protects it from damage that would occur if it ran dry. When you loose coolant, you also loose the lubricant additive that lubricates the compressor. The voltage to the compressor that you checked for will not be there as the low coolant switch has broken the circuit. Have the coolant system recharged and checked for leaks.

Thanks for your post , I spoke to a buddy mechanic and he indicated the same as your post. He suggested that I convert my AC system to 134a and use a additive to check for leaks , he also said that the leaks usually occure at the valves. What do you think ?