I have a celebrity model TONGA S made by leisure spas and I keep getting this message (HH). In the manual these two letters mean heater hot in excess of 118 degrees. That is not the case because the SPA shuts down within minutes of turning it on. I have looked at the SPA PACK housing and the heater is NOT hot at all.Could it be the sensor giving A false reading and shutting down the spa.?Is there anything else I can look at ?