[Spike.]

Check the red and yellow wires with a multi meter. On a VW the live with ignition and memory live is swapped over. On some wiring kits the red and yellow often have joiners in them, enabling them to be sawpped over is needed.

 

[Spike.]

Yep thats the one, the yellow and red have the joints in ready for swapping over as needed but…… I would be checking with a meter before just swapping wires over.

 

[Spike.]

Is there a little diagram on the radio casing itself? There usually is and you just need to match the plug wires to the diagram, it may involve cut and join and dont forget that it is an old van, somebody could well have been cutting and joining in the past to make another radio work.