ICE MACHINES Q-Model Service Manual

Section 6Electrical SystemIce Thickness Probe (Harvest Initiation)HOW THE PROBE WORKSManitowoc’s electronic sensing circuit does not rely onrefrigerant pressure, evaporator temperature, waterlevels or timers to produce consistent ice formation.As ice forms on the evaporator, water (not ice) contactsthe ice thickness probe. After the water completes thiscircuit across the probe continuously for 6-10 seconds, aharvest cycle is initiated.SV1730AFigure 6-20. Ice Thickness ProbeHARVEST/SAFETY LIMIT LIGHTThis light’s primary function is to be on as water contactsthe ice thickness probe during the freeze cycle, andremain on throughout the entire harvest cycle. The lightwill flicker as water splashes on the probes.The light’s secondary function is to continuously flashwhen the ice machine is shut off on a safety limit, and toindicate which safety limit shut off the ice machine.FREEZE TIME LOCK-IN FEATUREThe ice machine control system incorporates a freezetime lock-in feature. This prevents the ice machine fromshort cycling in and out of harvest.The control board locks the ice machine in the freezecycle for six minutes. If water contacts the ice thicknessprobe during these six minutes, the harvest light willcome on (to indicate that water is in contact with theprobe), but the ice machine will stay in the freeze cycle.After the six minutes are up, a harvest cycle is initiated.This is important to remember when performingdiagnostic procedures on the ice thickness controlcircuitry.To allow the service technician to initiate a harvest cyclewithout delay, this feature is not used on the first cycleafter moving the toggle switch OFF and back to ICE.MAXIMUM FREEZE TIMEThe control system includes a built-in safety which willautomatically cycle the ice machine into harvest after 60minutes in the freeze cycle.ICE THICKNESS CHECKThe ice thickness probe is factory-set to maintain the icebridge thickness at 1/8" (3.2 mm).NOTE: Make sure the water curtain is in place whenperforming this check. It prevents water from splashingout of the water trough.1. Inspect the bridge connecting the cubes. It shouldbe about 1/8" (3.2 mm) thick.2. If adjustment is necessary, turn the ice thicknessprobe adjustment screw clockwise to increasebridge thickness, or counterclockwise to decreasebridge thickness.NOTE: Turning the adjustment 1/3 of a turn will changethe ice thickness about 1/16" (1.5 mm).ADJUSTING SCREW1/8” ICE BRIDGE THICKNESSSV1208Figure 6-21. Ice Thickness CheckMake sure the ice thickness probe wire and the bracketdo not restrict movement of the probe.Ice Thickness Probe Cleaning1. Mix a solution of Manitowoc ice machine cleanerand water (2 ounces of cleaner to 16 ounces ofwater) in a container.2. Soak ice thickness probe in container of cleaner/water solution while disassembling and cleaningwater circuit components (soak ice thickness probefor 10 minutes or longer).3. Clean all ice thickness probe surfaces including allplastic parts (do not use abrasives). Verify the icethickness probe cavity is clean. Thoroughly rinse icethickness probe (including cavity) with clean water,then dry completely. Incomplete rinsing anddrying of the ice thickness probe can causepremature harvest.4. Reinstall ice thickness probe, then sanitize all icemachine and bin/dispenser interior surfaces.Part No. 80-1100-3 6-47