I have an Image renew 628 that we've had for almost 4 years. It seemed to quit heating so we replaced the heating element only to get a FL error. Replaced the pressure switch are and now seeing all kinds of weird things. I also pulled out the filter cartridge during this time. I can see the heater light come on, the temperature reading flashes, then may quit and then the temp starts adjusting up or down. I put a therm in the tub and it was reading 62*, while the control panel was reading in the 70's. My husband moved around a wire that was marked high limit assy and it would make the control panel go wacky again. Is this concidence or would our high limit/freeze switch be going out.

TIA
Jul

High limits go bad, but moving the wire shouldn't be a problem unless you've got a loose connection at the board. I wouldn't be too concerned about the temp discrepancy just yet.

So as of right now, what happens when you turn the tub on? Any errors? Still not heating?

Sadly we are now suspecting our circuit board. We by-passed it and the heater kicked on and the tub started heating. We let it run long enough to verify that the tub was heating.

Before by-passing the circuit board we disconnected the high limit wire and plugged it back in. We no longer got any errors, we no longer had the temp adjusting up and down (it was reading pretty close to actual temp) and the heater light was no longer coming on.

It's not unusual for a relay on the board to go bad so that an element only gets power to one terminal. This may have been your problem from the beginning. If you have a volt meter you can check the board before ordering a new one.

For 240v spas:

With the tub on and a demand for heat, test the voltage with one probe on each heater terminal. It should read 240v. If it reads 0v, leave one probe on a heater terminal and put the other to ground or neutral. If you get 120v you've got a bad relay. If it still reads 0v you may still have a bad board or a safety device that is not satisfied.