I have a 2000 chrysler grandvoyager se and it 's got a problem the air conditioner only works in full speed how can i fix this problem

You need a new heater resistor, l know you said A/C but if your fan doesn't work on any speed except high it is the heater resistor, located underneath the glovebox/ kickpanel area on the passenger side.

There is a blower resister,module ,it is bad,it is located near the blower motor,mounted on the outside of the blower case,but actually goes inside the blower box to keep cool,most of the time the blower motor is the cause for the resister to go out,the blower draws too many amps,even though it may seem it is fine,this is the cause for the resister failure.