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Just thought I'd ask in case anyone else has done this. I'm about to fit a P3 multi gauge and it comes with a cable that can be attached to automatically dim it for night time. I can't for the life of me identify the best fuse to use, especially not in the front of the car. It ideally needs to be something that only has power when the headlights are on (not the DRLs). Anyone any idea?

Many thanks,

Check the Grey/Blue wire on any of the vent connector. Pull any vent out and try that wire. Pretty sure the vents only light up when the rest of the car illumination comes on.

That'd be perfect, thank you, I will check it when I'm in there.

Unfortunately the Grey/Blue wire doesn't appear to have done the trick. I traced the wires back from the plug for the vent but I couldn't get any voltage reading across any of them, lights on or off. So, I took a chance and connected to the grey/blue anyway on the off chance it would come live when the light sensors switch, but it doesn't appear to. At least it doesn't dim the gauge.

Any other suggestions for something that is on only when the headlamps are on? I know there are fuses in the luggage compartment but it seems there must surely be something up front?

Many thanks,

did you measure voltage with ignition on?

morski wrote: ↑

Fri Sep 21, 2018 10:43 am

did you measure voltage with ignition on?

Hm, pretty sure I did, would be daft not to but you've got me thinking again now. I'll double check and post back, but I do have the dimmer wire connected to the grey/blue wire now, I've driven the car at night, and it doesn't switch the brightness (neither is the gauge permanently on the dim setting).

I'll let you know what I find.

Thank you.

Its definitely the correct wire, ive double checked the wiring diagrams. Same colour is used throughout the car for illumination. Check the ciggy lighter plug and it will be 3 wires +ve,-ve and this illumination wire.

Thanks for your patience with me Morski, it turns out it's working perfectly (when I enabled it in the gauge configuration). That'll teach me to skip read the instructions.

Much appreciated.