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Wiring In Oem Sat Nav Display Unit

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Hello all,

I'm trying to wire in an OEM sat nav housing unit into my car (which does not have the original sat nav wiring loom). I've followed P. Lindblom's guide on this (link), but when connecting the unit to the stereo power cables as he suggests, I instantly get a blown radio fuse.

I've also tried connecting the switched live and ground wires behind the cigarette lighter (i.e. switched live to the positive terminal on the cigarette lighter and ground to the negative terminal) with the permanent live again going to the stereo permanent live wire, but with the same result.

I'm using the original wiring harness that connects to the back of the sat nav module, and I have three wires coming out of the back of this harness (i.e. top right pin - permanent live, bottom right pin - switched live, bottom left pin - ground).

I have removed the OEM screen as I plan to install my own sat nav unit into the housing. Therefore, as far as I can see, the only thing inside the housing that would draw any current is the motor/solenoid assembly, but I doubt that this would draw more than 20A so as to blow the fuse. Does anyone have an idea what the problem could be?

Any help is much appreciated.



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Thanks for the tip. I'll have to take the casing apart to see if there's a short in there somewhere. I doubt there's any problem with the stereo power cabling because if there was, then surely I'd have the same problem with the stereo.

Perhaps I should have mentioned, the fuse blows instantly on completing the connection to the head unit. This is without even switching the ignition to the ACC position.

Out of curiosity, I replaced the standard 20A radio fuse with a 30A fuse (reckless, I know!) and then tried the connection again. This time the fuse didn't blow, but connecting the wires produced a lot of sparks (again with the ignition completely off). Would that also be because of a short?


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I'm pretty sure I've got the right wires - going by their colour codes and also the fact that connecting the permanent live and ground wires results in sparks and then a blown fuse...

I've taken everything apart in the nav casing looking for any sign of a short, but no joy. To isolate the component causing the issue, I first removed the wiring harness I was using, and connected the wires to the bare pins at the back of the control circuit board with spade connectors. But still the same problem - I connected the ground wire first, and then as soon as I connected the permanent live, the connection sparked for a moment and then the fuse blew. So it's safe to say that the harness isn't causing the issue.

I then disconnected the open/close and tilt buttons, and the motor from the control circuit board so the only component in the circuit was the control circuit board and tried again, but with the same result. Could something be wrong with the board? I removed it from the casing and inspected it, but all the pins seem fine and there's no visible sign of any damage to the board.

I'm really at my wit's end with this, and the number of new 20A fuses I've installed over the last few days is now flirting with the ridiculous... :tsktsk:

To top it off, my stereo isn't working now. When I plug the cable into the back I can hear the changer whirring so there's definitely power going to it - yet it doesn't switch on. I'm guessing maybe the Radio 2 fuse has blown? As I remember, that's in the driver's side footwell, which is a right pig to access...

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