A.O. Smith Flow Modulation / Minimum Flow Issue

A.O. Smith tankless water heater cycles on and off during use (temperature swings)

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Flow rate below minimum activation, Clogged inlet filter, Oversized unit for low-flow fixtures, Temperature set too high causing short-cycling

Safety: Turn off power and gas before cleaning filters.

1. Increase flow: Open the hot water tap further or use a higher-flow showerhead to maintain flow above the heater's minimum.
2. Clean inlet filter: Remove and clean the cold water inlet filter screen on the tankless unit.
3. Adjust temperature: Lower the set temperature so less cold water mixing is needed, which can stabilize flow.
4. Descale: If scale restricts internal passages, perform a descaling procedure.

Medium 3/5

Cold Water Inlet Filter Screen

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