I'm in the process of installing the MDI to my Columbus and would like to be able to keep the CD boot Changer working as well. (I know that I will have a 30Gb hardrive, iPhone playlists & a SD card so don't ask me "Why?")

The MDI is installed with a 'piggy-back' or 'pass-through' harness.

According to My GTI website, it is possible, but I'm confused.

Where do the cables from pins 5, 6, 11 & 12 actually go to?

The headunit (Columbus) or to the CD Changer?

Anyone know?

Pin outs 5, 6, 11 & 12 are all currently empty and are allocated a CD Changer Pass through.

Do I need to add new cables to these empty pins and run them from the MDI plug to the CD Changer?

Or remove the existing CD Changer wires from the main plug at the back of the stereo and extend them to the MDI plug?

If I were doing this, then I would dump the pass through cable completely. Remove the MDI connection wires from the passthrough kit by using a pin extractor and place them directly into the main quadlock behind the headunit.

But yes you can have MDI and the changer connected and functional at the same time.

Thank mannyo.

I think I understand - I should remove the long cable 'A' from the quadlock 'B' and put it in the correct place on the original quadlock (not shown below).

Does that then mean I can do away with the double quadlock 'pass through' adapter ('B' & 'C') supplied with the MDI?

The missing 'pass through' cables should be on the connector 'A' according to the My GTI website link (above). Would these then come from 'B' to 'A' or 'A; to 'C'?

yes, connector A goes through to C, if you can work out where C goes on connector A you may get away with removing the plastic block and transferring it to the original quadlock.

There are a lot of connections to A, so it maybe easier to do this and if there are other connections in the same block on the cars quadlock transfer these to to the MDI block instead.