My turn signal fuse keeps blowing,whenever I start the car or if I move the trans lever. The fuse cover shows number 12 but number 14 is the fuse that blows. The brake light still works but the horn doesn't. I need to find what else is on that circuit...number 14. I need a euro wiring diagram.

Fuse 14 powers:

Antitheft Alarm System
Automatic Climate Control
Auxillary Fan
Backup Lights/Transmission Kickdown
Engine Overload Protection
Horns
Warning System

Try unplugging the kickdown switch and/or removing the backup bulbs as a simple test of two those circuits. (Or start the car in neutral to avoid activating the reverse circuit). See if the problem goes away when those circuits are disabled. If the problem persists, check the other circuits on fuse 14.

If the problem is in the backup circuit, clean the fuse contacts and rear lamp socket connections with electrical contact cleaner. Corrosion at the connections can cause excessive current draw when you activate the brake lights and backup lights together while shifting from Park to Drive.

If after cleaning the electrical connections you find that the problem still persists in the backup circuit, you may need a new neutral safety switch. The backup lights have their relay in the neutral safety switch. The relay ends up failing after many years of use.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Here are a few causes to look for in old car wiring problems ,something was unplugged and done away with but wires were left untidey .Heavy parts ,etc ,etc gets thrown into trunks and is also known for leakey gaskets which begins the rust to dust issue (check grounds and these items in this area).Pulling through wires looking for other issues under the dash.Learn from the fuse box whats giving you issues, then consider the above.

Alec i could not have put it any better, than what you have just said .