Horn, reversing lights, fog light all not working

[mgbman]

I need some help please.

The van (1980 Devon 2l) has been off road for some months.

Did pre Mot checks today and found the horn doesn't work, the reversing lights don't light up and fog light not working.

Checked reversing switch connectors at gearbox, cleaned them up, checked with meter and continuity ok across switch terminals.

2 horns under van, cleaned up connectors, swapped connections, neither horns sound. Horn switch in steering wheel is original, 2 spade connectors there. put meter on them, no volts.

seems no live to the horn switch. Tried temporary earth wire to van body, still no horn. Bypassed horn switch, still no sound.

Replaced fuse 12 is that correct one.

Wiring a bit messy at the rear lights. Brake lights work, main lights work front and back. Indicators all working.

[Robsey]

Horn is fuse 12 ( 8 amp bullet fuse)
Rear Fogs is an additional fuse to the right of the fuse box. Also 8 amps.
Reversing lights are said to have an inline fuse in or underneath the the relay / junction box in the engine compartment.

Regarding the horn - try applying 12 volts directly across the horn.
If it is still silent, then it either needs retuning.
(Adjuster bolt on the back of the casing), or simply replace with another horn.