*PLUMBERSSTOCK EXPERT* responded:
Hello! Thank you for trusting PlumbersStock.com! If your tank does not deliver enough hot water, please follow these troubleshoot procedure. This procedure assumes line voltage, ECO, and elements are in working order. Turn power “ON” to water heater and set multi-meter to “Volts AC”. Adjust temperature setting of upper thermostat to the highest setting. The water temperature in tank must be below thermostat setting for this test. If the rated voltage is present, upper thermostat is calling for heat. But if the rated voltage is NOT present, replace the upper thermostat. Adjust temperature setting of upper thermostat to the minimum setting. The water temperature in the tank must be above thermostat setting for this test. Check voltage across terminals L4 and T4 of upper thermostat. If the rated voltage is NOT present, replace the upper thermostat. But if rated voltage is present, the thermostat is okay. Please refer to this here.