William replaced the gantry “end of track” proximity sensor along with the “lower boom prox”. The “end of track” prox tells the machine that the unit has traveled to the end of the track. If this prox is bad you will know because the gantry will not move but still run though a wash normally. The second prox replaced tells the “wash boom” when to stop the boom so it will not hit the end of its track. If this prox is bad the boom will be lower then normal and probably be pressure washing the ground. Both the sensors are located on the passenger side of the gantry.
This type proximity sensor used above is used in many locations in the Water Wizard. The Jim Coleman model number is 6626 and the Turck model number is Ni15U-EM18WD-AN6X-H1141 id number is M1634835 . If you want to look at all the Water Wizard parts for some reason check out this.