Hi there, my XJS Cabrio '94 seems to have moods with the horn in the steering wheel.
There are times when it works no problem(Maybe 2/10 drives it works) , however, most of the time it's not working. I'll add that all other electronics work.

Any suggestions on how to approach this and fix it so it works consistently.

Appreciate it!

 

The horn buttons are just pressed into the steering wheel.
Carefully pry them out and inspect, clean and test.
I have a few extras if needed.

 

Check JagRepair.com - Jaguar Repair Information Resource

Look for a horn relay. The 95/96 model years have one. It's the middle relay in a three relay assembly on the passengers side, under the hood. Not sure if the 94 works the same way, but I suspect it is similar enough.