I have a 1998 Sundance Optima 8 person hot tub with a Sentry 750/850 control board. When I turn the power one it turns on all the pumps and air and alternates between OH (over heating) and ice on the display. The temperature display sarts at 104 degrees and and with in a minute rises to 118 at which point the unit shut down. The actual water temp is about 40 degrees. When it started doing this a few months ago the water temp was in the 90s. Additionally I found chewed insulation from a rodent infestation.
Is this the sign of a bad control board or bad sensor or maybe a chewed through wire. I check the wires I could see from the front access panels.