Off side Lighting problem.

[Dazman9]

I Noticed today that both my off side side light and tail lights are not working, yet both bulbs tested good.
I've connected a multi meter to the rear circuit and discovered that when the lights are turned on, initially both these bulbs are only getting 7v, but after 10-15 mins this has dropped right down to 1v. From what I can see there is no fuse on this circuit. I have temporarily rectified this fault by bridging the left and right tail light circuits at the tow bar socket, though this is far from ideal it may stop mr policeman from having a chat....
Anyone have any theorys as to what may be amiss hear?
Secondly, does anyone have a wiring loom diagram I could use to try and find this fault.
Thirdly, is joining the left and right side lighting circuits together going to have any detrimental affects???  
Thanks 

Darren

[Tomcat3]

What vehicle do you have and how old ?????

[Dazman9]

Sorry, a 54 plate Desire Multispace HDi

[brodfather11]

If I recall correctly, each side is fused separately, ie  Fuse 18 and fuse 19 on mine according to the hand book which isn't always right regarding fuse positions and which circuits they protect .
   Look for a fuse blown.

Regarding the low voltage it may be a feedback from the interior light dimming.

[Dazman9]

My side lights/tail lights dont appear to be fused (or at least not with the rest of the in cab fuses or the engine bay fuses), and I dont have have an 18 or a 19, and anyway, according to the wiring diagram in the Manual I have, front left and rear right are on the same circuit, where I have both right ones faulty.
I've removed every fuse in the engine bay and all the 10amp drivers fuse's box and non of them affected the working (nearside) side lights.
I'l check out the dimmer, that may explain the low dropping voltage.

[Tomcat3]

As Brodfather says the lights are split diagonally so you are not left with no lights on one side or the other. You are looking for fuse 18 for the off/s rear tail light and front n/s side light and fuse 19 for n/s rear side light and off/s front side light. The n/s rear also powers the number plate lights. They are 10 amp fuses. Check the bulbs again as filaments can short across causing faults. Check earths and also check wiring on the towbar if you didn't fit it. There could be some dodgy spliced in wiring that could be failing.