Fuse 18 keeps blowing

I have a clipper cabby 1989, my main beam doesn't work nor does the blue light. However I notice fuse 18 keeps blowing when I turn the ignition on. Everything works xcept the main beam could it be a relay? I've changed the switch and traced as many wires as I can. It failed its mot on it.

Try switching the relay it could be shorting to earth

Which relay would you suggest?

MK1s don't have a relay for headlights. Thats one of the reasons they are so poor compared with modern setups.

I'd check no ones bodged an upgrade using high powered bulbs, wired spots direct to main beam or messed up a add-on relay install.

Ive check and it all looks completely standard, all th wires are correct and theres no hidious scotch blocs. I have heard theres a load reduction relay that can effect the main beam if faulty.

Are you sure the bulbs are standard H4s (50w?)

yeah, they have been working fine for 2 years!

Look into the headlight upgrade kit off flebay.. 35.00 ish,, sorted out my problems mate 
(I had issues with the yellow wire in ignition barrrel) 

fuse 18 supplies a coupel things with ign live, coolant level and horn relay mainly plus 2 of the ign live spades round the back of the fusebox. best get digging into the wires my man

I suspect I've pulled a wire off somewhere.