problems with audi

Hi, I have just tried to change the HU in my Audi A2 but have hit a problem. I am trying to replace the Standard unit with a Pioneer 5100UB. There does not appear to be any power reaching the HU when I turn the ignition on the unit is dead...when I unplug the ISO connector and plug it back into the factory HU then that works fine!! I have tried the 5100UB in my partners car and as soon as I connected it to the ISO and switched the ignition on it burst into life. I am very confused as the HU is obviously ok and the ISO connectors will power the factory HU just fine... Any ideas? I'm stumped... Thanks, Mark

Did you use the right harness for the car. Make sure you tied into the right wires. Also whats the brand and model of the harness?

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Hi, It's a 2004 Audi A2 1.4SE. I'm using the following adaptors,etc.. Fascia Adaptor: Autoleads FP 05 04 ISO Harness: Autoleads PC9 404 Aerial Booster: Autoleads PC5 52 Thanks, Mark

Even though this is hard to do, make sure your plugs are not mixed around. Otherwise you would be pulling your power from a speaker line. Try switching around your RED / yellow wires. Do you have a multi-meter at all? If so test continuity of the black wire to a ground point in the vehicle. Unplug the RCA connector for right now.