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Bob Minchin[_4_]

On 04/03/2019 21:13, wrote:
Vaillant ecotec plus 418 from about '07 or '10 or thereabouts. Pump stopped running, boiler gave error codes
F22 dry fire
F72 NTC thermistor value out of range
Pump sorted, but boiler won't run reporting F72.
Thermistors measured at 12k & 12-13k - I can measure them more accurately if needed.
Anything I should know or check before getting replacement thermistors?

NT

Resistances don't sound that far out. Normal criteria are not having a
resistance too low such that a few volts used in sensing does not
produce much self heating and yet the resistance is not so high to need
high impedance circuitry that can suffer from damp, dirt electrical
noise etc

The end result tends to be a working resistance around 10k