Lights not working

Kwakerman said:

In that case it would seem to indicate that there is a high resistance wire / bad or corroded connection in the supply leading to the switch. Ideally you need to find that 30A fuse and check the voltage on it with the lights switched on & off to see if it is constant, if it is that would indicate the header as being a the most likely fault (they are basically just big terminal blocks). That wiring diagram is for a 1999 TD5 so would expect it to be the same or very close.

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Do you know we're the terminal blocks would be ?? Deep in the dash I would expect !!!

Rob L said:

Thank you for the information and advice you have given me, I have checked the 30amp fuse under drivers seat and all seems good (checked with multimeter ) would a fault with the indicator/horn & highbeam stalk effect me been able to turn on side & head lights ??

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I wouldn't expect them to affect the sidelights but then again it is a Landy!

Rob L said:

Do you know we're the terminal blocks would be ?? Deep in the dash I would expect !!!

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Sorry I don't but suspect you are probably right. If you are sure you are measuring the correct 'power in' wire on the light switch and the 12v disappears when the switch is turned on then it is worth disconnecting the battery and measuring the resistance of the wire between the switch input and the 30A fuse output. It should read short circuit if ok, if it doesn't then either you are measuring the wrong point or there is indeed a poor connection between both ends.
If it is a poor connection, and you are feeling brave (and at your own risk because obviously I can't see what you are actually doing!) then you could try running a wire between the fuse output and the switch input (effectively bypassing the suspect wiring), if the lights then work you have proved the wiring fault and just need to find where the actual issue is.

I'm coming late to this, but I had a light failure problem a couple of years ago caused by one of my fuses suddenly acquiring a resistance of 70 ohms. So don't forget to measure the resistance of fuses rather than just their continuity. Similarly check for resistance rather than just continuity between the fuse and the switch. If there's high resistance it'll look like there's electricity there, but voltage and current will drop away once a load is applied.

Finally got to the route of the problem it was a bad live feed to the switch that controls the side lights & head lights, (possibly corrosion/bad connection) to solve it quickly the auto electrician installed a new fused live straight from the battery. Thank you to the guys on here that gave me advice and help much appreciated.