Towbar electrics wiring (relay bypass, not genuine)

[Umai Naa!!]

I'd say you're close to being on the money.

Stop/tail already shares one single filament globe. So why not share a wire on the output side? The Central Electrics module already steps the voltage up at the globe to differentiate between a tail light and a brake light. You do this using just one wire to the globe. The Central Electrics module already receives an input from the headlight switch, and one from the master cylinder travel sensor (AKA brake light switch).

[z1000]

Thanks Umai, is the central electrics model housed inside the light cluster?

Any idea how I can tap this single tail/brake line into a bypass relay to output tail and brake lines separately?

[Umai Naa!!]

Nope. Central Electrics module is above the fuse carrier under the right side of the dash.

I would tap into the feed from the headlight switch on the dash that goes to the Central Electrics module to get a tail light signal, and then do the same at the master cylinder travel sensor on the master cylinder for a brake light signal.

If you do it this way, you wont or shouldn't have any bulb monitoring issues.

For the trouble you'll go to to get it all working, you'll wish you got the genuine kit. Shoot me a PM if you decide to go down that path.

[z1000]

It looks like the bypass relay I got can take a single brake/tail input and output brake and tail lights separately. Give it a try I guess.

[z1000]

It turns out the relay I got (7 WAY SMART BYPASS RELAY - TOWBAR, TOWING ELECTRICS MULTIPLEX RELAY | eBay) has no problem outputing tail and brake light individually from a single tail/brake line in a MY12 model. No bulb failure has been detected, so far so good.

FYI this relay actually consumes power even when the car is switched off (as it is powered by cig charger in the boot), so I install an line switch in the boot sidewall to enable/disable the relay when required.