I have a 2007 mini cooper s and im looking to install a new after market head unit. I have everything apart and the wiring harness to the new head unit all hooked up. But the new head unit wont power on (tried three different head units) I tested the voltage with a volt meter on the constant and accessory. Both have power. But the unit still wont turn on. Im out of ideas on what the issue could be.

 

I don't know if this makes a difference or not, but does this car have the HK system? I've heard the HK stuff changes all the rules.

 

Its not an HK system (only has 6 standard speakers)

 

okay so bit of an update. i wired the constant and the accessory wires together (on the aftermarket head unit side) and got the unit to boot up. Now the issue is no sound. Will keep everyone updated once i figure out the issue.