Reversing lights working for the first time in 10 years

 I've had an issue with the reverse lights not working on my GT6 for many years, as it's not an MOT test requirement I hadn't bothered to fix it as it wasn't just blown bulbs.

Anyway I did a bit of investigation a few months back to try and sort the issue, strangely I was getting 12v at the reverse light in the rear cluster measured by my multimeter when in reverse but the bulbs were not lighting. I suspected a poor earth but cleaned everything up and it still didn't work. Then I bypassed the reversing light switch and it worked fine. I measured the resistance across the switch when it was in the on position and rather than zero ohms it was about 300 ohms, so basically the circuit was unable to pass enough current to light up the bulbs due to a faulty switch. 

As the gearbox tunnel has to come out to replace the switch I left it for now. Fortunately, reverse lights are not part of the MOT test in the UK so it wasn't a big deal that they didn't work. But with the issue I have with the speedo drive I've got the tunnel out and while waiting for a part from Overdrive Spares Ltd to arrive I decided to replace the reverse light switch. 

The switch is on top of the gearbox under the remote on my and needed the remote extension off to give decent access, I know some cars have it at the front of the remote opposite the overdrive inhibitor switch but mine has a different location for some reason.

Reverse Light Switch on top of the gearbox

Having replaced the switch and made up a reverse gearbox fresh wiring loom I went to replace the remote extension but had a few issues getting the gears to work. After asking some questions on facebook and messaging gearbox guru Mike Papwortth it turns out it was in 4th gear and I needed to get it into neutral to replace the remote. 

Gear selectors were in 4th position, I had to move the left selector backwards to align with the others to select neutral

I moved the selectors with a screwdriver to get them aligned in the neutral position and this allowed me to reinstall the remote extension to get the gears to select properly.  All sorted now and my reverse lights work for the first time in about 10 years.