Tub: Diamondback Spas with Balboa EL2000 system.

For some reason my heater is shutting off early. On the topside it is reading 104 but it definitely is not. I have the heater where the 2 sensor is on the heater itself.
I check the 2 sensor ohms and its both at 41. The heater element is at 10.9 ohms, and the heater is getting 240v. Im guessing the sensor is "reading" the temp at 104 and is shutting off the heater.
I tried unplugging the 2 sensors from the board and resetting it, but when i turn it on it still had a reading ranging from 91-104? Shouldnt there be no reading or an error code since the sensors are disconnected? Sometimes it will start with a 91 degree reading and in about 10 minutes it will jump to 104.

What could be the problem? Bad topside? Bad board?

Any help is greatly appreciated.

Thanks.

Is the water flow through the heater ok? Make sure you see water circulating in the tub while it's trying to heat (jets off of course). If that's ok check the board, front and back, for corrosion across the terminals for the sensor connections. You should get a sensor error with either of them disconnected so it seems like there's still conductivity across the terminals. If that's not the issue then I'd suspect the board.

if you have two sensors, one left and one right on the heater tube itself (M7 system), replace them both, reset the breaker to reset. If you only have one sensor on the heater tube, leave it alone and find the sensor that goes into the tub itself, and replace it.