Horn failure after ignition switch replacement
 

My horn only works with the ignition switch off after replacing the entire switch mechanism.

Turn the ignition switch on and the horn does not work.

Turns out I was sent the updated switch configuration.

I absolutely chased the failure to the new switch - horn works fine with the old switch plugged in.

Does anyone have experience replacing the original 986 switch mechanism with the updated one?

If so, was it a direct swap or were additional mods require to make it work?

Have you check the connection, It might be because of this. Which switch you have replaced with? Sometimes it may be due to a different configuration of the switch as it does not support the other configurations.

I've checked everything

With the new style ignition switch in, the horn works until the switch is turned to the run position

With the original switch in, the horn works with the switch in the off position and works with the switch in the run position.

Looking at the electrical diagrams in the Bently manual there is a change in the horn relay 2001 MY. It appears that the later model for the 7.2 DME may have added a diode and is directional where the earlier is not. I don't have a schematic for the later ignition assembly to compare to, but Maybe try an earlier Relay? Hey Particlewave what do you think

All I have to go on is the Bentley. Are you referring to the diode in the relay? That is just there to dissipate the EM field created by the solenoid in the relay...fairly common.
On both the '98 and '01 diagrams, the horn relay (and horns) get ground through a constant ground point and voltage from the current distributor (which is a direct connection to the battery). That voltage passes through the fuse panel (B3) and straight to the relay.

Neither of these diagrams show the ignition switch having anything to do with horn function.
James: I'd pull fuse B3 and test for voltage with ignition on and off, then go from there.

My 01S just had a horn problem. Horn worked with key out of ignition and stopped working when the key was in. Turned out there was a broken horn ground wire in the steering wheel. Once the wire was repaired, the horn works normally. Did you adjust the telescoping of steering wheel when replacing the ignition switch? My guess is this action led to my wire breaking.

Thank you. My 3-spoke steering wheel had the same horn issue, where it would only work when the ignition is off, with key out. I removed the airbag and saw that the ground wire broke off. I re-soldered the wire, and it is working now. The wire does seem somewhat worn, so I routed it the best I could to try to prevent strain to it.****

I investigated the motion of the wire as the telescoping function of the steering wheel is adjusted, and the wire does not move. I do not think adjusting the steering wheel puts any strain on the wire. The turning of the wheel could cause slight movements in the wire through. The clock spring is allowed 'play' in where it comes through the wire hole of the steering, so I think slight movements of the wire come about from turning the steering wheel. If it happens again, I will extend the wire slightly to relieve strain from it. None of the other wires seem to have any strain effects.