Heater comes on but dont heat the hot tub what could be wrong

SOURCE: Pool Not Heating Display Wrong

where the thermostat is located, the pump is not circulating the water

SOURCE: My Hot Tub gets and HL msg as soon as I turn it

This is probally a high limit warning. If you have a reset on your heater it is probally popped out. If you have drained the tub latly this may be caused by an air lock in the pipes and can be remeied by opening the drain **** on the bottom of the tub till you get water out of it. If your pump or motor has gone bad you will get these same simptoms. If you have no reset on your heater you may have burnt the element and will need to replace it This a symptom not the real problem. You need to check these other things first and be sure you have moving water before you try the heater. I hope this helped and good luck.

SOURCE: Hayward H300 heater runs but will not heat water

Your internal by-pass could be stuck open or the disc could be worn to the point of letting water pass too fast. Or your thermal control valve could be stuck open. These are both found in your water header going into the heater. Hope this helps, good luck.

SOURCE: My hot tub will not heat up. The motor is running

sounds like the heating element has gone to the next life,.....you can test it with an ohm tester,....MAKE SURE POWER OFF WHILE WORKING ON IT!!!! but no doubt it just needs a "heating element" cracklin joe

SOURCE: my spaform hot tub will not reach its temp ..we

if the heater tests out good, you most likely have a problem with the water temperature sensor. Make sure that the temp readout matches the actual water temp.. Sometimes the heater will think that the water is up to temp because the temp sensor is feeding the circuit board bad info. Check sensors, replace as necessary.