This evening I replaced the OEM stereo of a 1998 Jeep Cherokee XJ 4.0l with a Becker 7820 which I sourced from ebay. I have the exact Becker unit installed in my other car which I also installed myself.
The Jeep houses a factory Infinity amp setup and for this I had to order a specific wiring harness (AUTOLEADS PC9-407). The harness has plugs which mate up with the plugs removed from the factory stereo and the remaining wires I colour coded and butt connected to the plug that fits the rear of the Becker.
Having completed all the connections I switched on the ignition but there is no response from the Becker. The OEM stereo had a ground wire spade connected to the rear but the Becker has no connection for this. There was a loose black wire coming from the wiring harness, should this be connected to the ground?
Also, the Becker appears to have a different antenna connection so this was left unplugged for now. Does the antenna carry power to the head unit per chance?
I found the problem, it turns out the Jeep's ground cable needs to be connected directly to the ground terminal from the Becker (socket A, pin 8). So now there is power to the unit.
Only problem now is that each time I turn it on I have to re-enter the code and it loses all of it's settings.
I assume there's an 'issue' with the permanent 12v which I will have a look at once some skin has grown back on my knuckles...
Well I managed to sort the permanent 12v issue. Quite simply it turns out that Jeep have the ignition and permanent 12v wires the 'wrong' way round so it was merely a case of switching them over. Everything is sorted! Almost...
Now I've got it all up and running I can nit pick with the finer details. It seems that the new head unit is suffering from noise interference whilst the engine is switched on. There's a feint whislte/buzz which rises with engine speed.
I've tried to insulate the power leads as much as possible but it appears to make no difference. Any ideas?
Yeah, try grounding the head unit to the actual metal of the car (the closer to the head unit, the better) instead of having it grounded through the factory wiring harness.