Installing a Third Brake Light

An aftermarket CHMSL improves safety

By Tom Morr

Center high-mounted stop lights (CHMSLs) became mandatory for all U.S. street-legal vehicles in the mid-’80s. The Department of Transportation theorized that greater brake light visibility would assist driver reaction times, thereby minimizing rear-end accidents.

The Moss Third Brake Light kit includes a Hella lamp, a pigtail wiring harness, 4-way connectors, a magnetic base, and an adhesive-backed gasket for the magnet.

Many older cars come from the factory with small, dim brake lights—some seemingly designed by The Prince of Darkness himself. To improve brake light visibility for British sports cars, Moss Motors offers a retrofit CHMSL kit (164-005). This non-permanent system plugs into the existing wiring harness. The kit combines a Hella rear fog lamp with a magnetic base and a quick-connect wiring harness. Because the light mounts magnetically, it can be easily removed for car shows.

The illuminating facts are that this Moss Third Brake Light Kit is an affordable way to improve safety. Do-it-yourself installation is a snap.

1. Locate the junction of the taillight harness and the main harness (normally in the left rear corner). The brake light circuit wire should be either green with a purple stripe or white with a purple stripe (depending on model year). Disconnect the left brake light wire and replace its connector with one of the kit’s 4-way connectors. Also plug the black ground wire into the 4-way connector.
2. Plug the pigtail’s Lucas ends into the 4-way connector: red to the brake light wire and black to the ground wire.
3. Choose a high, centered location for mounting the light. Note that the magnetic base won’t stick to aluminum or fiberglass. For non-permanent installations, affix the gasket to the magnetic base to curtail paint scratches. Plug the light harness into the pigtail. Secure exposed wires with nylon ties as necessary.