Vaillant Cooling Resistor for aroTHERM & VWL Heat Pumps

It is the Vaillant coding resistor (often called a "code plug") that puts a Vaillant aroTHERM or VWL heat pump into Authorised Cooling Mode — the firmware state in which cooling becomes selectable in the installer menu. Without the resistor fitted, the heat pump operates in heating and hot-water mode only. Vaillant supplies it under part number 0020266328, and under the functionally identical and interchangeable part 0020269259.

It is used across the aroTHERM Plus VWL ../5 and ../6 series, the aroTHERM Split VWL series, and the flexoTHERM / flexoCOMPACT range when configured for active cooling. Always check your unit’s model-specific Vaillant installer manual to confirm the correct resistor part number before ordering.

Yes — we call this Verified Dual-MPN. Vaillant has shipped the cooling resistor under both part numbers (0020266328 and 0020269259), and we hold physical evidence the two numbers identify the same component. They are functionally and electrically identical and interchangeable. The part supplied here works in any installation that calls for either number.

Fitting the resistor is only half the job. Once it is connected, a Vaillant-approved installer must enter the heat pump’s installer menu and enable the cooling function in the settings. The resistor puts the firmware into Authorised Cooling Mode; the installer-side setting actually switches it on. We strongly recommend involving a Vaillant-approved installer for both steps.

No. Radiators are heating-only emitters — too little surface area to absorb useful heat, and any cold radiator would just collect condensation. To actually deliver cooling, the building side needs a Fan-Coil Cooling Loop: a closed chilled-water circuit feeding fan-coil units that catch condensate in a built-in tray. The work to add that, alongside the existing heating system, is what we call a Cooling-Ready Retrofit. Ask a Vaillant-approved installer to quote one before assuming cooling will work.

Vaillant merchants typically retail this part at £100 or more. The price here reflects genuine surplus stock sold direct. The part itself is the same OEM Vaillant component supplied in factory packaging — there is no difference in the part, only in the price.

Yes. This is a genuine OEM Vaillant component, supplied new in sealed Vaillant factory packaging with the part number printed on the bag.

We ship worldwide using Royal Mail tracked services: United Kingdom £3.99 (Tracked 48, 2–3 working days), Europe £12.99 and the rest of the world £15.99 (International Tracked, 5–14 working days). You choose your delivery region at checkout and receive a tracking number when the parcel is dispatched. Orders are dispatched from the UK within 1–2 working days of payment.

We accept returns worldwide. Let us know within 30 days of delivery; the resistor must be unused and in its original Vaillant packaging. The buyer is responsible for return postage. This is in addition to your statutory 14-day right to cancel under the UK Consumer Contracts Regulations 2013 for online purchases. See the Returns page for the full policy.

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