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Having an issue w/ a Laars endurance Combi boiler. Nat Gas.
Customer complains about inconsistent hot water output... also was/ is getting the F4 error.
Manual says to swap out the sensor in the boiler (2400-445) I did that and still the issues persist.
Issue also appears to be intermittent... Runs fine when I am there then shows up later.
This is the newer version grey/ gold jacket.