Low Warning
d.72 on Vaillant ecoMAX

Your boiler's pump is running longer than it should to cool down the system after heating water, usually because a sensor has detected a temperature imbalance.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Hot-water pump over run

What causes this fault?

This fault occurs when the boiler detects an unusual temperature difference between the water leaving the unit and the water coming back in. The most common cause is a faulty or drifting temperature sensor providing inaccurate readings, which trick the boiler into thinking it needs to run the pump longer than necessary to cool down. In some cases, it can also be a sign that water is not circulating as freely as it should through the heat exchanger.

DIY fix possible

Check that all radiator valves are open to ensure good water flowTurn the boiler off at the main switch, wait 30 seconds, and turn it back onCheck the system pressure is between 1.0 and 1.5 bar

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Related fault codes

F.20View →F.24View →d.71View →

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