Heating and water heater fault codes

Choose your equipment. Each table shows only codes confirmed in a manufacturer document, states which models that document covers, and links to it. If you are unsure what your light means, start with how to read furnace blinking light codes or use the decoder.

Gas furnace

Tankless water heater

Commercial gas water heater

Ductless mini-split

Not seeing your brand? We add brands only after we have read the manufacturer's own code table. Check your owner's manual or the label on your equipment. Honest coverage beats a long list of guesses.