2001 jeep cher, compressor will not run and blow cold air inside cab, unless I use a jumper on the low pressure switch. do I need to replace switch or is it safe to run with jumper.

 

the sw is there for a reason. id make sure its good or change it.
when i was low on freon mine would not turn on, till i added some. then the pressure got up to normal. if yours dont , something else is wrong and you may cause more trbl by forcing it

 

It's also possible the switch is bad. (If the AC blows cold air there has to be some refrigerant in the system. But I would not take a chance running it that way.)

What you'll probably want to do is check pressures with a gauge set. The 1999 service manual states that there is no continuity in the low pressure switch if pressure is under 20.5 psi. (2001 is probably the same.) So if you have less pressure than that when the system is at rest, the compressor will not turn on.

As long as there is some refrigerant present it's OK to briefly jumper the low pressure switch to check operating pressures or charge the system. Just bear in mind that the compressor depends on oil carried by the refrigerant for lubrication so you never want to run it if the refrigerant charge is extremely low or zero.