A.O. Smith Water Heater Error Code 4 Flash: How to Fix It

Error Code

4 Flash

Brand

A.O. Smith

Product Type

water_heater

Severity

Critical

DIY Difficulty

Medium

Estimated Fix Time

45-90 minutes

Tools You'll Need

• Flathead screwdriver
• Multimeter
• Non-contact voltage tester
• Insulated tools
• Flashlight

How to Fix Error Code 4 Flash

1. Turn off power to the water heater

   CRITICAL: Never work on an overheated water heater while power is on. Risk of severe burns and electrical shock.

2. Check the temperature and pressure relief valve

   If the T&P valve is actively discharging large amounts of water, do not proceed - call a professional immediately.

3. Inspect the thermostat settings

   Use insulated tools and ensure power is off before touching any electrical components.

4. Reset the high limit switch

   Only reset once. If the error returns after reset, stop and call a professional.

5. Check heating elements for shorts

   Ensure power is completely off and use a non-contact voltage tester to verify before testing elements.

6. Inspect thermostats for proper operation

   If you're not comfortable testing electrical components, skip this step and call a technician.

7. Restore power and monitor operation

   Stay nearby during initial restart. If the 4 flash error returns, immediately turn off power and call a professional.

Parts You May Need