my hot tub doesnt always stay hot. it will work fine but sometimes when you checkit it isnt hot ,the heater doesnt kick on if you turn the pump on then the heater will kick on and heat it, but then it will later have the same problem. I have replaced the pressure switch on the heater thinking that was it but no.it seem a little better but not rite. the oressure switch is adjustable 1psi.-5psi. I just adjusted it till the heater came on. worlking it back and forth till it seem to turn on the heater.I'm thinking now maybe the low pump relay is sticking and not circulating the water those the heater will not turnon . if you have any advise on trouble shotting this problem please let me know.