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Laars Endurance issues

kcopp Member Posts: 4,305
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.


  • Chris Alonzo
    Chris Alonzo Member Posts: 41
    Did you ever resolve the issue? I am getting an intermittent F4 error. This is accompanied by a banging noise and the pressure gauge jumping up and down. I turn the unit off and on and the problem goes away. I have tested the sensor with an ohmeter and it tested good (1.4K ohms). I am wondering if the sensor is only failing when it gets hot inside the unit.
  • kcopp
    kcopp Member Posts: 4,305
    Did not. The owner ended up having someone replace the boiler.
    Chris Alonzo
  • Chris Alonzo
    Chris Alonzo Member Posts: 41
    I am suspecting insufficient water flow causing the water to flash boil and the high  temperature of the water causing the sensor to go out of range. I measured the amperage of the system pump and it is double what it is supposed to be. So, I am leaning towards changing it.