I have a strange problem. When my standard Visteon radio / CD player died, I ordered a new radio, a Sony MEX-BT3900U. If I plug the power ISO with that of my Fiat it doesn't work. Of course, because I have read on this forum that the red and yellow wire must be connected to each other.

If I do that, I hear the mechanics of the CD player working. But when I attach the front panel, the display isn't working. I can load a CD, and pushing the eject button the cd comes out, so the front panel does make contact. I call Sony and they say, that it means a defective front panel. Now I got sent a new radio, but exactly the same problem! Again, no display.

Now I'm confused. Would the voltage may be the issue (too low, too high?)
Someone else an idea?

(I have not tested the radio in another car, to see if it works then (unfortunately, no one nearby has a standard car radio installed).)
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IIRC You have to do something a little different with the power for Sony Radios. I cant for the life of me remember what your supposed to do though.

Not very helpfull as such, but thanks any way ) Maybe you (or some one else) will remember?

Solved! The yellow and red wire from the radio both have to be connected for the display to work. Just the red will give power, but doesn't really turn the radio on.