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Volkswagen aerial selection control unit / diversity information

Early models of the Mark V had a aerial selection control unit (diversity) under the right front seat to select the strongest signal, in later headunits this function was performed by the headunit itself.  Swapping headunits to or from cars with a diversity unit requires installation or bypassing the diversity unit.

An external diversity box is required for the following models

  • All MFD2 CD versions introduced week 10/2005 until week 45/2005 when the MFD2 DVD version replaced it.

The headunit performs the diversity function on the follow models

  • All MFD2 DVD versions introduced week 22/05 (it is possible that DVD versions fitted between 22/2005 and 25/2005 have the external diversity box but as so few were shipped I haven’t been able to confirm this)

If a car has the MFD2 CD version with the aerial selection control unit (diversity) under the right hand front seat and has a headunit with the diversity function built in installed the aerial selection control unit (diversity) needs to be bypassed which will be covered in detail further down.

On the rear of the headunits there are two antenna connectors.

On cars from week 45/2006 (unverified) the connectors are

HF1 (white) – left aerial module
HF2 (beige) – aerial amplifier

On cars prior to week 45/2006

ZF (white) – to aerial selection control unit
HF (white) – from aerial selection control unit


1 – Transparent connection for FM aerial input signal from aerial selection control unit
2 – Beige connection for FM aerial output signal to aerial selection control unit (diversity)
The aerial input signal from connection 1 is checked in the radio navigation system and the result is sent via connection 2 to the aerial selection control unit. If the aerial signal being received is too weak, this then switches to a different aerial (diversity).

Accessing the aerial selection control unit

Before beginning dismantling work, perform the following steps:
– Switch off ignition and all electrical consumers and remove ignition key.
– Slide front right seat to rearmost position.

– Remove cover under seat in direction of -arrow-.


Release and disconnect connectors -A-.


Remove clips -arrows- and control unit.


Bypassing the aerial selection control unit

The unit under the seat has two connections from the aerials, both are HF and are converted and sent onto the new headunit as a HF/ZF signal.

There are two ways to bypass the diversity box.

Option 1 – bridge connectors

Bridge the connectors internally in the box.

Option 2 – adapter cables

vw_diversity_system_adapter_1The specs on the cables are below and they can be purchased from ebay or ecommerce sites that specialise in Fakra cables. who sells the following adapters for ~AUD$25 per adapter (2 required)

Antenna extension adapter Fakra (m) Cable 0.1 m
Extension Fakra (m) to Fakra (m)

Fakra (m) connector with universal Z-Coded Case
Fakra plugs fit all different colored Fakra plug, since this is universal coding
Low loss coaxial cable RG Brand 58 (D = 5mm)
Made in Germany


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