Triumph Repair: TR6 Horn repair, horn button, ground wires

Question
i had a Superior steering wheel installed on my 1972 TR6 back in 1979. The
horn stopped working some time ago but I recently decided to trouble shoot
the problem. Using the repair manual I located ground wires that needed
repair and cleaned all terminals. Now the horns blow but only with the
ignition off. If I insert the key and turn to auxiliary and or crank the engine
the horns will not work.  If I remove the key the horns will work; but only
after waiting a few moments.  I did not change any connections under the
dash or on the steering column. It seems like the turning of the ignition key
shorts out the circuit but I don't understand since the purple fuse circuit is
live all the time??????  

Answer
Check the horns for power when the key is on. If they are powered then short the horn button wire with the key on to see if they blow. If they do check the horn button to see if it grounds ok.
If the horns are not powered with the key on look at your wiring diagram and use a test light to see where you lost power.
Always do your testing when the system is in it's failed mode.
Howard