Mk2 Audi A3 8p wiring harness fault

[Vagnut123]

Hi there I'm a complete noob to sites as normally can fathom most scenarios but this one has me flummoxed so here goes,

Been tinkering with cars for years and the odd stereo every so often but all had simple iso connectors until now... bought a mk2 audi a3 8p a couple of years back for my wife and a few months ago the standard stereo packed up (power fluctuations) so had a look about and picked up an brand new A-sure unit (now regretted) which has a quadlock fitment which is handy as the A3 is also a quadlock fitment harness but since fitting sed unit I get no power/sound to the rear amp/speakers, pulled the harness back out and only have front speaker cables fitted in the harness no rears which means the cars got the factory fitted amp which runs both sub and rear speakers...

loads of videos for dual iso plugs in the mk2's which have basic coloured wiring but nothing for quadlock, also I have spoken with a-sure (too no prevail) they said I need one of two wiring harnesses and sent me a link to both (neither are correct)... Also cant find anything on wiring diagrams for my a-sure unit

Is there a simple bypass/rewire procedure that can get power/sound to the rear amp???

Thanks mark.