If the heater produces a small quantity of hot water check the lower thermostat and heating element.
Dual element water heater thermostat.
A dual element water heater is a two thermostat system an upper and lower that heats water in its tank one element at a time.
Single phase 240v and 230v non simultaneous dual element water heater thermostat wiring.
A dual element water heater uses two heating elements controlled by two separate thermostats.
For use in 2 element water heaters replaces apcom style thermostat.
Tod style upper element thermostat.
If you detect voltage replace the heating element.
The upper thermostat takes first priority heating the water to a preset temperature before powering up the lower thermostat to heat the water to its final temperature.
Test the thermostat with a voltmeter and replace it if you don t detect any voltage.
When it reaches a specified temperature.