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Number Plate Light Bulb Fuse Blowing Constantly

rear number plate bulbs fuse 4 blowing shorting

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#1 Lew_VRS


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Posted 31 March 2012 - 11:12

Hi All,

A quick one.. my car passed it's MOT the other week no problem (thank God) everything fine which is expected as i've spent some dough on it in the last year.

Now coming home the other night my friend driving behind me said 'your rear bulbs are out' and to my surprise they were.. whipped the trims of the bulb covers (after much swearing + rounding of corroded self tappers) Both bulbs intact.

Fuse 4 in my fuse box 5A had blown.. which controls the rear plate bulbs. There was a small build up in the fuse holder of that fuse of some white gritty sort of stuff.. gave it a clean and replaced the fuse which immediately popped when I turned the sidelights on again.

Now I know it isn't to do with the washer pipe toward the rear (as this has disconnected at the washer bottle).. All I know in the rear is that my CD player stopped working after pushing it down too hard. I don't suppose the CD Changer comes off the same fuse?

Aside from that I'm stumped. Suppose I'm better of whipping the already rattling rear boot trim off the tailgate and checking for a poor earth or shorting of wires.

Anyone got any suggestions? I am an ex auto electrician so competent with testing tools.. I'm just being lazy and hoping someone else has had the same problem and can give me a starter for 10 before I start tearing the rear end of the car apart.

Cheers :)

#2 moley


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Posted 31 March 2012 - 12:45

Somewhere there is a dead short to cause the fuse to blow immediately. I would check all the bulbs and bulb holders first, a poor earth will show up as a dim lamp.

#3 Lew_VRS


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Posted 31 March 2012 - 16:41

Right.. got fed up in the end.. pulled the boot trim off belled out with my multimeter both sides of connector brown/black going to ground both sides.. no problem and no sign of the other violet/green wire going to ground either side.

popped a new fuse in with all of the bulb holders/harnesses loose with no problems whatsoever both bulbs working then keeping the sidelights on I decided to build it all up again and moving the wires back to their original position it blew again.. obviously rubbing somewhere but without another pair of hands wobbling wires whilst I bell it through I wont be able to find the location.

I will update as and when