controlling heat

[morax]

my tub recently had heater element go bad so replacement was tuff to find found one simsliar but the t wells where different size so i got thermostat as well. now my tub has hugh temp changes it doesn't turn heater on till it 93 to 95 and doesn't shut off heater till 107. checked for air pockets none found.my tub is old and all the spec on new parts are the same.any ideas please help tub season coming to an end

[Gary]

The old mechanical thermostat were calibrated for 104F max but had a tolerance +/-2F. You could have received a new defective thermostat or you are getting ambient temperature on the probe.

On the old style thermostat is a good idea to use some heat sink on the bulb and seal the end of the dry well to keep ambient temperature out.

[Vinny]

You guys use that crap too. I hate heat sink compound!