NB: These instructions are given for guidance only and cannot engage the author's liability in the event of misinterpretation, failure to assess the vehicle's actual condition and/or non-conformity, unsuitable mechanical practice or the use of inappropriate tools.
Twin horns — Voxbell or FIAMM-type.
As standard, these twin horns are fed directly from the left switchgear button. Acceptable with a new contact, this arrangement becomes troublesome as the contact wears and oxidises, because the current it has to carry is high.
Another common fault: the second horn is fed through the first. If the contact is slightly worn or dirty, the current is insufficient and only the first horn sounds, or the fuse blows, or one of the horns fails internally (usually the one fed by the other).
The solution: fit a relay to relieve the switchgear button and give the horns an adequate supply.
Relay wiring
- Terminal 30: battery +, via a 20 A fuse.
- Terminal 87: supply to the horns (both in parallel; their other terminal to earth).
- Terminal 85: to the horn button on the switchgear.
- Terminal 86: earth.
This way the button only switches the relay coil (low current), and the horns are fed directly from the battery through the relay's power contact.