Water heater powers on but display shows E0 and unit will not start heating

Safety first: Turn off the water heater at the breaker and close the cold water supply valve before removing any covers. Confirm no voltage is present with a multimeter if you are trained to use one.

Steps to check:

• Remove the front access panel to expose the control area on the CTC water heater.
• Locate the display/user interface board and the low-voltage harness that connects it to the main control PCB.
• Inspect the harness plugs for looseness, corrosion, or bent pins. Reseat both ends of the harness firmly.
• Check for any signs of moisture intrusion or burnt components on the user interface PCB and main control PCB.
• Restore power and see if the E0 code clears. If the code persists, disconnect power again and test continuity of the harness if you have a meter.
• If the harness tests good and there is no visible damage, the most common repair is replacing the user interface PCB. If that does not resolve it, the main control PCB is likely faulty and should be replaced.

When to call a professional: If you are not comfortable working around live electrical circuits or removing control boards, contact an authorized CTC service technician.