john T Posted April 7, 2020 Report Share Posted April 7, 2020 my coleman horizon 400 spa heater not turning off. I set temp to 80 but heater heats water until high temp sensor shuts down spa (usually around 110 degrees) sn1 and after a while after cooling I get the OH code and than I can restart the spa. But, the heater seems to continue to operate. I hear a hum from the heater area as if the heater is always on. I shut down the whole spa over night to cool. When I turned on the spa again, the heater got hot to touch pretty quickly - the water temp this morn was 104 degrees at startup, the hight temp sensor triggered again. any idea. hope you understand. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted April 7, 2020 Report Share Posted April 7, 2020 Do you have an electrical tester? Open the control pack and post a pic of the circuit board. With the temperature set below actual temperature, test voltage going to the heater. If you have voltage, you have damaged relays on the board. It must be repaired or replaced. If the relays are not under a plastic cover, you can see the points and might be able to manualy free the stuck relay(s) with a screwdriver. Be sure power is off before you start poking around with a screwdriver. With power off, all relays should be open. 1 Quote Link to comment Share on other sites More sharing options...
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