Horn honking by itself when driving - argh!

started the other day when i picked up the van to move house after having fuel injectors changed. its a 1995 kzh hiace with an aftermarket momo steering wheel.

Its bloody terrifying driving constantly honking at people..... only a matter of time before some road rager lynches me when i pop to the grocery store.

what can i do? any quick fix?

The horn is behind the front grille, you should be able to locate it and disconnect it temporarily while you sort out the issue with the contacts at the steering wheel.

i took out the horn fuse this morning as a quick fix because the grill is a pain to get off

Well when I had a Fiat car I got told the way to drive it was to have one hand on the horn button and one foot on the 'go' pedal. Maybe your van has a similar idea and just wants to save you the effort of honking? Does everyone move over for you?
Automatic horn: the Japanese think of everything!

Two things you need to establish , is it wiring fault or horn button assembled incorrectly , does the horn work on positive or negative some things like door light switches work on negative . if it works on negative grounding its probably a wire that is shorting to the body use a test light .