I own a hot tub that is about 12 years old. It has a Gecko control pack. Here's what happens: From a power off condition...I switch the breaker on and the tub starts up. There are no error codes and the temp reading seems accurate. Lets say it starts at 65 degrees since its been off for a day. The tub runs fine on high and low and after a few hours of heating up it reaches whatever temp I set it at. Usually 100 degrees. Now here's the problem. When the tub stops at the set temp there is a noise which sounds like flowing water or air in the pipes. Something of a swishing sound. The pumps are not on. This lasts for about ten seconds and then the error code comes up on the display. I have the 3 dots flashing. Then the tub never goes back on and doesn't heat the water. I have replaced the pressure switch numerous times and readjusted it with no luck. I also replaced the temp probe (it doesn't have a high limit switch) because I get a red LED display on my circuit board when the error occurs and was told it was the temp probe gone bad. That obviously did not help. All the jets and outlets seem to work and flow fine and don't feel like they are clogged. Any ideas what this could be and how to fix? I appreciate any help or comments. Thanks!!