# Why won't my Vaillant heat pump cool?

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

The common reasons a Vaillant heat pump will not run in cooling mode, from the missing resistor to installer-menu settings and system design.

Common reasons a Vaillant aroTHERM or VWL heat pump will not cool:

- No coding resistor fitted — cooling cannot be enabled at all.
- Cooling not enabled in the installer menu after the resistor is fitted.
- The home has only radiators — no emitters that can deliver cooling.
- Controls not set to request cooling (mode, schedule or set point).
- The model is heating-only and not cooling-capable.

Several checks are installer-level — use a Vaillant-approved installer.

Shop: https://www.vheatc.site/