Hi limit sensor

We have a spa and the display is showing 42 degrees and the OH code.
We need to know which part we need to replace.

5 thoughts on “Hi limit sensor”

  1. Suzanne, if you take an external thermometer and place it in the filter bay compartment towards the shell of the spa do you get a reading 42 degrees Farenheit or do you get a different reading higher or lower and if so what is that reading?

    1. Suzanne check that the grey smart heater attached to the side of the Sentry Control box is not overly hot to the touch. If it appears to be roughly the same temperature as the spa water you may have a bad temp sensor. That at least would be a good component to rule out first. If you would like to be sent a link to see the part you are looking for price and availability please send me the serial number of your spa.

  2. We changed the thermostat on Sunday.
    I set it to 38 degrees last night and today it is hitting that temp.
    My husband thinks we need to change the hi limit sensor. Would that be the next step?
    The grey smart heater doesn’t seem to be hot. But the spa is actively heating.
    Would someone be able to call me and walk me through this?
    My number is 204-894-0391

    1. Suzanne this is a web based only support site. If you replaced the temp sensor and after that the temperature in the spa with your external thermometer is reading 42 C and the topside control panel is reading 42C/OH this could mean there is an overheat condition. The OH message typically displays when the hi-limit sensor in the heater thermowell senses a temp of 116 degrees F or more or if the temp sensor reads a temp of 110 degrees or more. The OH message typically goes away when the temperature in the spa drops to 106 F (41.1C) or less. If the actual temperature in the spa was colder then the topside control readout or if the temperature in the spa water was cooler to the touch this would typically mean you could have a bad temp sensor. When the actual water temperature matches the topside control reading and you have an OH msg this most times is due to an obstruction in the circulation line and or a soiled filter. Check your circ lines and flow switch for obstructions. Obstructions could be anywhere from your filter right back through your circ pump, heater, flow switch, mazzei injector, off gas chamber and drain fitting. Clear the obstructions if any are found, cool the water in the spa down with cold water and see if the temperatures match up again without the OH msg. In some rare cases a bad hi-limit sensor could also cause the OH msg when the temperatures match up. If there are no obstructions and it is not a bad hi-limit you could have a bad PWA. If you would like a link to our website for parts required/availability and prices please send me the serial number of your spa. If all else fails contact our Service Support Desk to book an in home diagnostic and repair of your spa.

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