I'm about to replace my stock head unit with a Pioneer unit. The car (Merc) has an ISO connector and according to everywhere I've asked/checked I should not need any adapter to connect to the Pioneer head unit. The problem is that I'm not getting any power to the head unit. I've checked with my multimeter that there is power running right through the wiring and plugs. I notice though that there is a connection/wire on the Pioneer for positive power from the ignition. I've checked some wiring diagrams online for ISO connectors and this seems to be missing from the ISO connector on the car side. I have constant (negative) 12v at pin 4 and negative(earth) at pin 8. What I don't have is ignition 12v at pin 7 and I don't see one anywhere in the wiring loom connected to the (car side) ISO connector. I notice that a hands free kit that was installed has basically used the constant (negative) 12v to supply both negative 12v feeds to the car kit. Is there any reason why I should not do the same thing with the head unit - that is : supply the pin 7 ignition connect with 12v from the pin 4 constant 12v ?