Mack,
Figure 6 in the manual seems to indicate there are switches that are normally open when the jacks are all up. Wires 522, 525, 528, and 531 are Full Retract inputs to the ECU which would then drive the All Up LED. The each of the 4 switches will be in the Open position when the associated jack is fully retracted. What the manual doesn't show is the location of the switch but I think it is fairly safe to assume it is on/in the jack assembly. Assuming the wire numbers are on the wires going into the ECU, they should also be on the wires at the jacks.
Steve