Hello,
I have a older hotspring highlife model K spa serial# K 391484 (unsure what year saw aug 1989 on relays). I went outside to check on the chemicals and found that the heater was up to 108 degrees (had set at 90 for months) and wouldn't shut off, same with the circulation pump just stays running when the heaters are turned off. I pulled down the control panel and took a look around to see if I saw any thing obvious which I did not. Turned the power back on and the thermostat switch was responding now but the circulation pump will not shut off. I'm sure I need a thermostat but I know there has to be something else going on causing that circulation pump not to turn off such as the tub safety switch. I tried testing the tub safety switch with some hot water I microwave and the heater reset switch tripped but nothing happen with the tub safety switch. Id appreciate it if someone could lead me in the right direction.
Thanks
Dustin

Tub high limit trips at 120 degrees. Heater high limit trips at 150 degrees. Most likely, you have a "runaway" thermistat. Your circ pump only runs when spa is calling for heat.

I cleaned my thermostat switch with some contract cleaner and has been working good so far. I have another problem which I'm sure is contributing to the overheating which is the tub jets come on by them selves. I woke up this morning and heard the tub running so I'm willing to bet I have a bad jet switch also.

Also I Emailed a person at backyardplus and they said that my circulation pump is suppose to run 24/7 which I honestly never noticed it running when the heater was off so I'm a bit confused about that.

First the jet pump coming on...Is there a timer mounted into the side/front of the control box? If so, a pin or two may be in the position where the pump will turn on by itself. As far as the circ. pump and whether it runs 24/7, I thought the spa was early enough where it only ran on demand, I'll check a schematic tommorrow.

Nope no timer box. So far for the past 2 days the tub has been perfectly fine and stays at a steady 92 which is where i have it set at. The circulation pump is still on so still unsure if its suppose to but as long as the tub stays at a steady temp and jets don't turn on by them selves I'm happy.

You have a 3rd quarter '89 Highlife.
The circulation pump can heat the water, by friction, to 108 if the spa is not used for a long time. In that spa it would take a month of non-use in the summer.
The circulation pump does run 24/7 on that year spa.
If your temp is 92 the click in the thermostat should be somewhat low on the dial. Turn up the t-stat slowly and listen for a relay click and see where it is on the dial. The colder the water the lower it should be on the dial.
It's possible you had a stuck relay that fixed itself.
Sometimes you can turn up & down the t-stat so the relay clicks many times.
This can kind of clean the relay contacts and un-stick the relay.
Hope this helps if it's not already fix ed.

For the spa turning on by itself. I would first try loosening the front control screws. Careful they are nylon/plastic and break easily. Make sure the jet button springs in & out and is not sticking in. You might also try turning the jets on & off many times to loosen a relay that might be sticking. Other than that I would think Jet Switch, not too hard to do.