ok i have had this royal spa hot tub for a long time, been a great spa. at the end of last winter the tub starting tripping the high limit switch, so i closed it down until this fall ( aka NOW). I adjusted the water parms and put in a new filter, turned the thermostat all the way down and turn the temp control on the control panel to 1/2, filled it up and turned it on, i then adjusted the temp at the control panel until it reached 103. all was running well, i thought i may have imaged last years problem. closed the lid and went to bed. i woke up the next morning and nope, the high limit switch was tripped once again, i reset it and the temp on the panel read 102, i have determined that if my lid is off or half open then the switch does not trip. i have tested this. if i close the hot tub cover the temp reading on my control panel shows a rise if i inspect it moments later, and if i leave the lid closed the HL SWITCH TRIPS every time. so high limit means heater is working and its getting to hot. so i disconnected the circulation pump and aloud water to rush back thru the heater, my thoughts was to flush out any junk in the line outta there,water flow on my tub is cir pump, into heater into filter and out to the tub. anyway i put an ohm meter on my heater element and got 14.5 ohms, i changed the filter, fired it up, closed the lid and ran into town; about a thirty minute trip. came back and the HL switch was tripped and i had to wait about 15 mins before it would reset, i turned the tub back on, left the lid half way open and it has been running for two hours wide open, WITH if i close that lid it will overheat and shut down..... Having the lid opened or closed should have 000000 TO DO WITH or cause AN OVERHEATING ISSUE. hHELP ME PLEASE.