Mk4 aftermarket CD fitting problem

[OP]

I'm in the process of replacing the Gamma CD and cassette units in my 01 Mk4 with my JVC unit. However when I plug the ISO into the back of the JVC unit it doesn't work. I have 12v and switchable 12v at the unit via the ISO connections but it'll not switch on. I know the JVC works as it was in my old Mk4 Polo, which it just plugged straight into. I've re-fitted the original setup and all works fine.

Anyone got any ideas as to why please?

[Rhyso]

might be some info in this thread

http://uk-mkivs.net/forums/t/177496.aspx

[OP]

might be some info in this thread

http://uk-mkivs.net/forums/t/177496.aspx

Cheers mate, looks like it may hold the answer 

[dubber36]

Also the fuse in the back of JVC headunits can be fitted in 2 different positions depending how it's wired.