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Loss of LH side/tail lights


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Hi

I am calling on the collective wisdom of the forum, as it is now persisting down and I have given up for the night!

The fuse for the LH side / tail light circuit has blown. The previous owner has put in a 10A fuse instead of a 5A so this might be an indication, or not, as I have had the vehicle for 3 years or so.

If I remove all of the lamps, and test for resistance between the live terminal and earth at all positions, I get an open circuit reading on the multimeter (MM).

If I take out the blown fuse and measure between the load side of the holder and earth Iag a reading of 1.2 Ohms on the MM.

I am thinking that the wire has been damaged somewhere between the fuse box, and the point where the front and rear feeds split off.

Does anybody know where this connection point is?

Vehicle is a 1997 300tdi 110 station wagon.

Thanks in advance

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the loom for the rear portion is on a multiblock by the drivers side bulkhead, (all rear loom is seperate down inside of chassis rail box). you could try unplugging here and see if it's a greater resistance.

not sure of colour could be red/black. May also feed the number plate lamp as well.

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Pete

Cheers for that.

It is a place to start tomorrow, but the fact that I am getting the same readings front and rear, makes me think the problem is closer to the fuse box.

I think the feed has been cut / shorted, as all the "consumers" show infinity to earth with the lamps removed, including the numberplate lamps, whle the fusebox shows 1.2 ohms. ( Note I said lamps instead of bulbs to avoid upsetting the electicians here!)

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red/black trace from fuse box to front left side light then along chassis loom to left rear tail light, also has a take off feed for trailer left tail light,

the chassis loom appears right rear inner face of chassis then up into area behind rear light cover panel, the left hand lights have a sub section going across the chassis rear cross member to left rear corner.

possibly the loom has been trapped or damaged during a fuel tank remove/refit or rear cross member repair.

if you have a tow socket fitted check inside for wire shorting out against each other/water ingress.

300tdi wiring diagram below.

post-20-0-04810000-1415050759_thumb.jpg

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If you have checked the above and pulled multiplug to disconnect the rear loom and pulled the bulbs from the front and it's still low resistance it may be worth checking behind the dash tray, the loom comes up behind the dash vertically before exiting behind the plastic cover centrally on top of bulkhead which splits many ways. Left for headlamps/sidelights/heater/wash wipe etc right for headlight/sidelight/brake fail. then you have some for engine block/glowplug timer. Then some thicker ones for rear loom multiplugs.

It is possible to trap the loom behind the metal heater box/dash or it may have worn through with age/vibration.

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Pete

Cheers for the additional info.

Sods law is in operation.

I went back to the car this morning, and the fault has gone. :hysterical:

I bridged across the terminals in the fuse box with a 55w bulb, and it did not light.

I tried the side lights ad they worked.

I swapped the bulb out for a fuse, and all is well, after much waggling of wires to see if I could get it to fail.

I'm guessing it will be ok until it starts raining or snowing at night when the fault will present itself once again.

Thank you all for your suggestions.

Mike

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Have a look in both the rear wheelarches, where the loom exits the body under a flap and crosses to the other side(why do they do that?). Mine had rubbed through both sides, same age & type of vehicle. Also, if you have a socket for towing that has to be high up in your suspect list. Both of these are easily checked out. The wiring at the back underneath has a pretty hard time of it, so probably worth looking over it all. It seems insane that's it's not all within the body to me, OK it might not be dry, but it would be a bit cleaner.

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