AO Smith code 991 Solution for error code 991 Check the gas type of the water heater. Inspect the environment around the water heater. ... Check if there is grease and/or dirt in the burner (Part #101) and the fan motor (Part #103), especially if the water heater has been installed in a contaminated area. Error code '991' for type ATI-110C-N by AO Smith. Cause and ... More help here, but you probably need a service call, especially if it is a gas water heater.
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AO Smith code 991 Solution for error code 991
Check the gas type of the water heater. Inspect the environment around the water heater. ... Check if there is grease and/or dirt in the burner (Part #101) and the fan motor (Part #103), especially if the water heater has been installed in a contaminated area.
Error code '991' for type ATI-110C-N by AO Smith. Cause and ...
More help here, but you probably need a service call, especially if it is a gas water heater.
https://www.google.com/search?q=error+code+of+991
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