Thread: Help: Wiring and fuse

A bad earth point introduces more resistance into the circuit, meaning less current, meaning no blown fuses. What you should be looking for is a point where your positive cable is making undue contact with earth BEFORE reaching the load (either the front park light or the tail light).

The fuse should have been 5A originally, but there's probably no reason to read anything into that. As you have LED lights the fuse MAY be able to be reduced to a lower value, but I would stick with 5A.

So, how do you start searching for the problem. You have three things on that circuit: the park light, the tail light and the trailer connector feed for its tail light (if you have a tow bar fitted). First, check the light fittings themselves. Pull them out and unplug them one at a time and see if that fixes the problem, then take a good look at the trailer plug connector. Trailer plugs are often wired by the apprentice, so they are regularly done badly. If it's none of those things, get ready to dig through the wiring loom, including to the dash indicator. Fun times ahead.

+1 on the trailer connection,

The purpose of the fuse is to protect the wiring from damage during a short circuit condition, not the device hanging off the end of the wire.

I'd be following the wiring looking for chafe points or maybe checking for shorted out lamps on the circuit.

If you have a 20 watt (ish) test lamp you can put it across the fuse holder. Start putting your paws on wiring, disconnecting things, wiggling looms - when the lamp goes out or dims, you have found the short.

Originally Posted by Spudlynicholas

If you have a 20 watt (ish) test lamp you can put it across the fuse holder. Start putting your paws on wiring, disconnecting things, wiggling looms - when the lamp goes out or dims, you have found the short.

Hi,
I would have thought when the light goes to full power you have found your short circuit. But all that has happened is the lamp has come up to full power. This saves continually replacing fuses while you are trouble finding. With the lamp across the fuse block, your other globes in the circuit won't be getting full current either, so they will be not as bright as normal.
If the light goes dim or goes out, no current is flowing via the fuse block and the circuit is open. You have found a break in the wire some where.

cheers

Current can track across plastic through a rust stain (in a light fitting) to earth as happened with my bull bar mounted indicators. As has been said rig up the bulb in the fuse holder. Take all the bulbs on that circuit out, switch on, then one by one put the bulbs back in whilst observing the behaviour of your 'fuse bulb"

Had exactly the same problem on my 2002 defa110 ,tried everything as well. Had me beat. Took to auto elec and he couldn't find anything wrong as well touch wood. Hasn't played up since Sorry I know it doesn't help you