# What is a Vaillant coding plug?

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Updated: 2026-05-22
Language: en-GB

Explains the Vaillant coding plug — a resistor in a connector housing that signals an option, such as cooling, to the heat pump controller.

A Vaillant coding plug is a connector containing a fixed-value resistor that
configures an appliance option. The controller reads the resistance as a setting.

- The cooling coding plug (0020266328 / 0020269259) authorises heat pump cooling.
- Coding plugs need no programming and survive power cuts.

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