The MGA was fitted with a horn as standard equipment, wired into the car's positive earth electrical system. Over six decades of service, original horns commonly suffer from corroded contacts, weakened internal windings, and tone deterioration, leaving many cars with a weak or intermittent note. This category covers replacement horns and horn upgrades suited to the MGA, alongside the relays and wiring components needed to fit them correctly.
Positive Earth Considerations
Every MGA left the factory with a positive earth electrical system. This is the single most important factor when selecting a horn or any electrical component. Some modern horns are polarity-sensitive and will not function correctly, or at all, on a positive earth car unless wired accordingly. Cars that have been converted to negative earth require components matched to that configuration.
Confirming the car's earth polarity before fitting avoids the most common cause of a non-working horn.
Single and Twin Horn Arrangements
The MGA's horn note can be restored with a direct replacement of similar specification, or improved with a matched pair of wind-tone horns producing a fuller, two-note sound. Twin-horn arrangements typically draw more current and benefit from a dedicated relay so that the steering-column push operates the relay rather than carrying the full load through the original switch contacts. This protects the switch and gives a more consistent note.
Relays and Wiring
Adding a relay is a common and worthwhile upgrade, particularly where higher-output horns are fitted. The relay isolates the horn-push circuit from the main current draw, reducing voltage drop and preventing premature wear of the horn-push contacts. Correct fuse protection and wiring of an appropriate gauge ensure reliable operation and protect the wider electrical system.
Originality and Restoration
Owners restoring to original specification will want a horn matching the period type and note, while those using the car regularly often prioritise volume and reliability for modern traffic conditions. Both approaches are catered for, and the choice depends on whether the car is being returned to factory specification or set up for everyday road use.