Installing a Headlight Relay Kit in Triumph TR6

I Recently finished upgrading the headlight wiring of the otherwise original harness in my 1972 Triumph TR6. During the car's restoration, I removed the harness and used a multi-meter to test every circuit and rewrapped any frayed or damaged parts with harness tape before reinstalling.  I did however want to improve my headlights and that involved upgrading the lighting circuit.   I contacted Dan Masters at who at that time was offering a complete rewiring kit but his Headlight Relay Kit was not available so I purchased a kit from Moss Motors-Europe, the part number is GAC40254 and includes 4- Lucas SRB520 relays.

I opened the box and this kit is really a kit…completely unassembled, wires, relays, connectors, blade fuses and instructions, figure 1.

figure 1.

Recently an additional relay kit has come on the market that is less ambitious to install.  It is available from Victoria British and installation seems very straight forward.

To start the installation of the Moss Motors Relay Kit, obtain the necessary tools, including: a Multi-Purpose 6-1 Tool (figure 3) to cleanly strip the wire and although not essential, a British bullet connector crimping tool, available from British Wiring, and a good quality soldering gun.  The instructions (figure 2) refer to “lucar” connector terminals; I have always known these as “spade” connectors, so to keep this narrative consistent I will refer to “lucar” connectors in this article.  The bullet connectors provided in this kit can be soldered onto the wires resulting in a solid fit. The solder is flowed into the connector from the top.

Moss Motors 
figure 2

It would have been helpful to have photographs included with the included narrative assembly instructions.
(figure 2)


Much of the time spent installing the kit is fitting the appropriate connector to the proper wire.   Items 2 through 4 and 16 through 21 and Items 25/26 in the Instructions can be completed at your workbench.  It was necessary to convert from meters to feet as the instructions are written to European specifications, and although ample lengths of wire are provided in the kit remember to measure twice and cut once. 

In the photograph below, you can see that the lucar connector is crimped using a Multi-Purpose 6-1 Tool, over the wire plastic and the stripped copper wire before soldering.

figure 3. A Multi-Purpose 6-1 Tool will find lots of uses in your tool box. 

All the connections were crimped then soldered using rosin-cored solder.   This solder can be purchased at a local electronics or hardware store, (figure 4) be sure you have a powerful enough soldering gun so the heat is only applied to the connections being soldered for a few seconds, wicking the molten solder into the connection.   

Although not specified in the instructions I also used a layer of heat-shrink tubing to insulate the connector where it attached to the wire (figure 5).

 solderfigure 4

Heat Shrink tubing
figure 5.

A recommendation is to use multiple layers of heat shrink tubing to aid in supporting and protecting the wire at the soldered end.  However, any additional layers of heat shrink tubing on the wires that snap into the relay holders would make them too massive to fit.

The relay holders lock together with the fuse holders, Item 15 of the Instructions and begin to take shape.  See figure 6 below.

relay holders locked together
figure 6.

Cutting rubber spacers
figure 8.

Once the fabrication and assembly of the components are completed it was time to move to the car. Remove the battery, the two stay rods, the radiator shroud and the overflow bottle: this allowed me to better locate and identify the original wires in the harness.

The best part of this kit is that the original harness is not cut or modified; rather a new circuit is installed into the current harness.  The instructions have you locating a suitable position for the assembled relays, Item 15 in the instructions, and to drill and mount them.  I used double sided-tape to position the assembled relays during the routing of the wires in the engine bay.  Once I was comfortable with the location and positioning, I permanently mounted the relays using machine screws and nyloc nuts instead of the metal screws provided in the kit. 

 To improve the fit of the relay against the engine bay compartment, I used a piece of heavy black rubber cut to size as a shim (figure 7). This was installed behind the relay holder and shaped to fit the inner front wheel well.

Figure 9 shows the mounted relays with a great view of the rubber spacers installed behind the relay holders.

rubber spacers behind relayfigure 9.

mounted to wheel wellfigure 10.

 wire from relay assembly
figure 11. Ground wire from relay assembly.

Included in the kit is plastic sleeving to cover your wires with after you cut them to length. (figure 12) You will have to pull the wires through the sleeves because if you try to feed them by pushing through the sleeve eventually friction will prevent their passage beyond a few feet. Obtain a small length of thin solid copper wire and run that through the sleeving first then tape it to the wires that go through the sleeve and pulled them through.

The “Black” ground wire from the relay assembly was installed onto the bolt that secures the driver side stay rod, eliminating an additional hole that had to be drilled into the bodywork.(figure 11) See Item 31 in the Instructions.

The “Brown” live feed wire was routed along the driver’s side of the engine bay, following the original harness, then tucked behind the wiper motor behind the top of the battery and then down to your selected power source.  I secured this wire against the firewall using plastic clips."

ffigure 12.

The clips were then attached to the firewall with aluminum pop-rivets, (figure 13).  I think this presents a clean installation that properly secures the wire.

relay fig.9Figure 13.

Engine Bay with relay kit 
installedFigure 14.