A Quick Word About.........Retro Fitting a Reversing Light Switch

I’m currently working on the gearbox and clutch and have taken the opportunity to fit a reversing light switch to the gearbox. A reversing light is non-original to my 1968 car, but is a small concession I’ve decided to make in the interests of safety. I don’t want anyone stuffing into my rear end when I reverse!  

Reversing lights were introduced in late 1971 for the 1972 model year. Virtually the entire range seems to have received this upgrade - with only the humble 'D Special' missing out in Europe. Though even the D Special got them in other markets - such as Australia.   As factory-fitted, cars have two reversing lights mounted below the rear bumper.

From the factory, cars had two reversing lights (Photo from Aussiefrogs)

Personally speaking, I find that additional lights hanging off the bumpers tend to make the DS look a little lumpen and heavy - as they interfere with the lines. My car is a Pallas and I know that some people feel the same way about the excessive Pallas rubbing strips and trim. 

On a four speed box, the switch is screwed into a cover on the end of the gear box and is operated by the movement of the reverse gear fork shaft when the car is put into reverse. I have a couple of spare, later four speed gearboxes. The photo below is of the gearbox I took the switch from. 

With the cover removed, you can see the black mark on the end of the shaft where it presses against the switch pin.

The reverse gear operating shaft presses on the switch pin

The casting that includes the thread for the switch is similar to - but different from the casting without switch. It has extra ‘body’ to allow for the threads that receive the switch. 

Reverse gear covers: without and with reversing light switch

Although the switches themselves are readily available, I don’t think it would be possible to tap an older cover to fit a switch as there would be no ’shoulder’ to provide depth for thread and the switch would be mounted too close to the reverse gear operating shaft.

Casting has raised section to provide thread depth

For the five bearing engines with four speed boxes, the switch and cover swaps straight over between later and earlier models and can easily be removed if I start to have sleepless nights about tampering with the cars original spec.

Reversing switch fitted

I don't know about arrangements for five speed gearboxes. As only the D Special missed out, maybe all five speed cars had reversing lights as standard anyway?

So fitting the switch was quick and simple...........I just need to decide how to wire it up. Cars with factory fitted lights had a couple of extra wires built into the loom. They come out of the loom at the same point as the oil pressure switch wire and the water temperature sensor wire. One of these wires (the mauve) is the power feed - which comes from the ignition switch. The other (the yellow) takes the power from the reversing switch to the reversing lights at the rear of the car. 

September 1971 Wiring Diagram: Part 62 is the reversing light switch. 

Part 25 is the oil pressure switch. Part 13 is the temperature sensor

I'm yet to fit it, but I bought a new front loom last year. As a direct replacement for a 1968 loom, it doesn't include wires for a reversing switch. As a power feed I may, instead, try and pick up power from the 'Bob' terminal of the voltage regulator but, as I will have to route power from the switch to the back of the car anyway, I may try and discretely run an extra wire from the ignition switch. I may tape it into the loom. 

The circuit diagram above isn't strictly accurate: a short, shielded flying lead (about 105cm long) with two spade ends connected the switch to the front loom. I've got one of these, but might make a new one up.

Flying lead for reversing light switch

In terms of the reversing lights themselves, two brands were used: 'Cibie' and then 'Gelbon'. I'm told the Gelbon lights are smaller (and so less 'lumpen'??) than the Cibies. There are a couple of other good, retro-looking styles available (including 'Gelbon' copies) at a reasonable price and brackets for fixing any lamps to DS bumpers are available from the usual suspects. 

'Lumpen' or not, I will probably just fit one reversing light - leaving my options open for a fog light or extra stopping light on the other side of the bumper.