Furnace displays E7, often with erratic temperature readings or short-cycling

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Defective NTC return sensor, Damaged sensor wiring, Poor thermal contact between sensor and return pipe

Safety first: Turn off power and let the system cool.

Locate the return temperature sensor on the return pipe entering the boiler.
Check that the sensor is firmly attached and properly insulated from ambient air.
Inspect the wiring harness for cuts, abrasions, or loose connectors. Reseat the plug on the main PCB.
Test the sensor resistance if possible and compare with the ATAG specification. Replace if out of tolerance.
After replacement or reconnection, restore power and reset the unit to clear the E7 code.

Medium 3/5

ATAG NTC return temperature sensor

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