Hi, I have been fitting an aftermarket Head Unit in my son’s 2008 NC. I had done this very successfully in the past with my own NC. All was going really well, the new HU working fine etc. I took out the HU to change the DAB aerial and when I put it back all was dead. On turning on the ignition, the DSC, TCS lights are on and all needles sweep up to maximum then down to zero. It looks like I MIGHT have shorted the power-antenna wire as I was pushing the HU back in, though I am not certain. Anyway have now disconnected the HU completely but the warning lights are still coming on. Strangely the fuel gauge needle is not going down to zero even after the ignition is off. The car starts fine. No obvious fuses blown.
Update, it is actually the Engine warning light and TCS which are now on and strangely when the ignition is turned off the temperature gauge and rev counter do not return to zero.
I don’t have a wiring diagram of this, but it sounds like it might be a broken/loose earth connection of a shared earth tag where these items should all be grounded together. The only thing to do is remove the head unit again and have a careful look with a good light for a floating wire or bunch of wires (black ones I think.)
Amazingly all sorted. It was due to a blown fuse 5 in the main fuse box - the one that covers “Interior Light and anciliaries”. Cleary that extends to causing the gauges and dashboard lights to behave in a bizarre way including a complete needle sweep when ignition is switched on!
I remember a similar post about a fuse blowing and causing the gauges to be erratic. Yes have been known to cause a few sparks myself from not disconnecting, as you say lesson learnt.
Needle sweep, an update - managed to get full sweeps of the speedo and rev counter needle gauges at start up in a 2007 NC.
I changed over the incandescent festoon interior bulb for an LED but in doing so must have shorted the fitting (battery not disconnected!)and found there was no power to the lamp, radio, boot light. DSC and TCS lights remained on.
Traced the problem to a blown 15A fuse in the main fuse block, position 5, “ROOM”. Replaced fuse and then restarted - ignition back to normal no needle sweep and no lights.
I understand from previous postings that this fuse is removed when the cars are in transit from Japan to minimise battery drain - might be worthwhile removing this fuse when car is not in use for a week or more to prevent battery draining - one drawback is that the radio loses its memory and needs fresh settings, but better that than coming back from holiday to a flat battery in an airport car park.
Incidentally, if you do disconnect the battery*, the DSC light will come on until the system has recalibrated itself. You can just drive the car and the light will go off when next restarted (which is what I did) but I believe you can also do it by turning the wheel lock to lock and back again.
*or, in my case, leave the boot ajar in rhe garage, totally flattening the battery
I’ve just done exactly the same thing and thought the needle sweep was pretty cool, but I’ve also got an issue with the boot not opening with the key fob remote or button under the steering wheel, and I’m unable to lock the car using my key fob remote … The “Room” fuse is definitely blown so i will need to replace that, but could these extra issues be something else? I’ve got a 2008 2.0l Sport model. All my local car parts shops are closed for the evening, and its not the same shape as the 15amp Aux fuse to try a swap and test.