Coronado is hard on anything mechanical. Salt air works on venting and gas connections, and the units themselves often sit in snug garages and side yards where nobody looks at them until something goes wrong. A tankless can run for years like that, right up until the morning it starts flashing a code.
Inside the unit, hard water does its own damage. Minerals settle out as scale in the heat exchanger and the unit has to work harder until the shutdowns start. Outside, salt air keeps working on the venting and connections. Either one can be what's behind the code on your controller.
We'll get someone out to look at both, and you'll get a straight read on whether it's a descaling, a part or a replacement. If it's a replacement, it gets sized to your household and the space it has to live in. You decide, on your timing rather than the unit's.
