I have a Saratoga Spa(Polo) with a AquaTherm spa pac. The heater element stays on after I turn the pump off. I have to turn the thermostat all the way off to keep the heater element off. Otherwise, the element stays on an boils the water in the heater jacket. Then the high limit switch trips(which is good), protecting the unit. Is this a problem with the pressure switch? The heater thinks that water is still flowing....???

Yep. It's either a pressure switch or a flow switch. That said, it's not a good thing to let this situation continue... I mean, if the high limit fails... then you'll end up with a much more expensive repair - (a new heater etc).!

Thanks for the quick reply. I located the pressure switch. While attempting to remove the wires from the terminals, the whole switch fell off into my hand. Water started leaking from the heater jacket. This is not good since the spa is indoors on the second floor of my house. I was alone and could not get to the garden hose to begin draining the spa. I had to hold my finger on the leak. Luckily, I had a pencil behind my ear, and I jammed it into the hole! Now, I will have to disconnect the spa pac to access the area where the pressure switch goes.The pressue switch is a Tridelta Model 3029. After all this, I'm almost certain the problem is the switch. I can see where corrosion took it's toll. I will have to locate one. I will let you know how it goes.

You may have a stuck heater relay as well.
What luck with the pencil!!

Problem Solved!