Azel DS-60 Dual Temp Gauge - Inaccurate temp reading

My recently installed dual temp gauge is always reading 233 degrees F. on the OUT display. This probe is located 170' away on my EKO water jacket. I swapped the IN and OUT wires on the back of the unit and the problem switches so I know the problem is in the wiring or sensor probe. Azel provided me with the resistance / temperature chart for diagnosis. I removed the OUT wires from the unit and measured 4.75K ohms. According to the chart this is about 110 degrees. My EKO display was showing 112 which is very close. Some how the wiring is causing a problem but I can't detect anything wrong with my fluke 87 multimeter. I pulled the 18 gauge speaker wire through my buried plastic conduit. I did notice some water / moisture in the conduit but I can't see how this is causing my problem since my resistance is correct. I also double checked and made sure the wiring was not running parallel to any electrical wires. The IN display works perfectly. This doesn't make any sense to me. Only thing I can think of is the Azel unit may be using a higher voltage output than the fluke causing a breakdown in insulation. Maybe I need to use a megger to apply a higher voltage to the wiring. I have one of these for checking motor windings but its at work so I haven't check it with that yet. Any ideas?