Horns Troubleshooting

Trouble:

How operate the horns ?

Note that : horns can only be operated when the ignition is on this means turn the ignition switch clockwise ONCE

horns fuse

1) The first thing I had a look at was the horns fuse located in the fuse board lying underneath the steering wheel. Testing the horns fuse with a multimeter set to Ohms indicates a (near to) 1 level which means continuity.
But check could have also been done visually as we see the wire inside the cartridge fuse is intact.

Checking contact switch at the steering wheel

2) Second check is the one of the contact switch located at the centre of the steering wheel. This is described in the N-3 section of the Workshop Manual. as follows :

1	2	3
4	5	6

1. Remove the gear selector cowling, which is in two pieces, by unscrewing and removing the six Phillips setscrews located in the cowl lower half; the upper section of the cowl is secured by the four outer setscrews and the lower section by the remaining two setscrews.
2. Unscrew the three nuts sitting behind the steering wheel and remove the horns button assembly from the steering wheel centre.
3. Withdraw the horns contact plate and disconnect the electrical plug.
Once the push button has been removed (4) You can see the contact plate connected to the ground by its three big screws (5) and notice the black lead at the middle of the plate which is connected to the generator (6).
Testing the push button using the Ohm position of a multimeter : 1 indicated by default goes to 0 when pushed shows continuity. : It was OK when pushed very strongly.
In fact, the problem was the centre button being wrapped by black false "leather" (see 3). This cover added extra thickness on the inner side of the button that hampered a good electric contact. So now this contact problem is [SOLVED] as to the main horns button.
Another thing to be looked at by the way is the earth brush whose purpose is to ground the horns by applying a contact on the steering column.

Contact brush. Purple/black wire is the horns colour as mentioned in the wiring diagram	Solder was added in order to correct an continuity problem..

But despite of this, main horns still operates intermittently

That's puzzling. In fact, after several days of trying every possible thing, I tried this switch here, at the bottom right of the fascia.
And it was the solution.
This switch activates the "city horns / country horns" option. It is reported to be an uncommon option, but an original standard Rolls Royce feature.
It allows you to choose between the snail shaped horn and the air FIAMM air 1horns. Both are situated under the bumpers.

Now, the FIAMM horns

3) At that point, the Italian pneumatic horns do not operate. They probably are activated by the floor button switch (at the right hand side of the headlamp switch) that is intended to operate the horns.

The FIAMM horns compressor.

1	2 horns relay. No way to remove cap..
3	4 blue circuit activates the relay coil / red circuit feeds the horns

(1) At the rear of the compressor there are two connections on for the ground (black) and one for the generator (red/light-blue). The metal bit is for a hose.
(2) The relay in a five pin relay but (numbers as printed on the relay cap have to be translated). This is how it is plugged (3).
The connector at the foreground feeds both circuits by forking ut what I DONT understand is that these two circuits are thus CONNECTED ???(yes they are I've checked it with the Ohmmeter)

Testing the unplugged 5 pin Relay

1*(85)->2(86) passes through coil pretty good continuity	3(30)->5(87) is not connected no continuity	3(30)->4(87A) is connected by default continuity
The 1 to 5 digits are known as ISO, and used on ISO relays

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Scotty Kilmer's