Volvo FH4/FM4 Voltage Converter 24V To 14V 21255317 7421255317 5904703623175 Auxiliary Power Units (APUs)

Description:
Genuine Volvo 24V to 14V DC voltage converter removed from a late Volvo FH4/FM4 Euro 6 heavy commercial vehicle. This module, OE reference 21255317 (also referenced as 7421255317 in some catalogues), is used to step down the truck's 24V electrical system to a stable 14V supply for auxiliary equipment and onboard electronics. The finned aluminium casing acts as a heatsink and is designed for installation inside the cab or electrical compartment using the integrated side brackets.

According to Volvo and commercial vehicle parts catalogues, part number 21255317 fits Volvo FH4 and FM4 series trucks from approximately 2013-on with Euro 6 engines. It is a genuine Volvo OE unit, not an aftermarket copy, and operates with 24V DC input and approximately 14V DC output. Typical applications include powering 12–14V accessories and sensitive control modules while maintaining reliability in harsh truck environments.

This specific converter was removed from a running vehicle and was function-tested prior to dismantling to confirm correct output voltage and stable operation. The housing shows only light cosmetic wear and minor marks from previous installation; the connector body and pins are intact with no signs of overheating or corrosion. No repairs or modifications are visible. Item is sold as a bare module only; existing wiring harnesses, fuses and mounting bolts are not included and should be reused from your original installation where possible.

Professional installation is strongly recommended. The converter should be mounted securely to a suitable metal surface to ensure correct heat dissipation and connected only according to Volvo wiring diagrams. Incorrect wiring or overloading can damage the unit and vehicle electrical system. No programming is normally required, but always follow Volvo workshop procedures.

This used OE converter offers a cost-effective replacement for a failed 21255317 unit while maintaining original equipment quality. It is supplied with a 3-month warranty and is ideal for fleet operators and workshops maintaining Volvo FH4/FM4 Euro 6 trucks.

Shipping & Returns:
We ship across UK/EU with tracked services. Returns accepted within 30 days; buyer pays return postage. Please inspect upon arrival and message us with any concerns.

Why Buy From Us:
Genuine part, 3-month warranty, fast dispatch, secure packaging.