Opened the spa about for the winter about a month ago and I have been battling an overheat issue. Spa has a balboa circuit board (not sure model but it has the telephone style plug ins for the thermastate and a dial stle controller on the topside)

First thought was stuck relay, so I replaced both relays (240v heater). Thought I fixes it but the Problem still occurs. The temp was at 101, I tried to bump just a touch and it shot to 105 in 24 hours, I tried to turn it down at it countinued to 110. There is a indicator light on the top that turns red when it is calling for heat. The temp keeps raising even when light is off. The heater must not been on all the time because I am getting a 4-5 degree increase in 24 hours. Normal increase for me is 6 degrees per hour when I refill the tub. Outside temp has been below freezing at night.

Any thoughts?

Steve

Your main pump sounds like it is stuck in low speed 24/7.

Try powering it down for 15 seconds or so... then power back up and see if the behavior continues.

Your pump is heating the water because it's not shutting off -

A normal consequence of pump operation.

Before I replaced the relays it seemed like the pump was always on. AFter I replaced them the pump does shut off after it's 4-5 hour filtration cicle but it does come on periodically throughout the day eventhough the water is to hot.