I'm in the enviable
position of using a base '60 S' 6R running the 1.2 12v (CGP) engine. OK with it's 60bhp I'm not first away from the lights, but its economical and keeps the miles and salt off the *other* cars during the winter 
However the issue I have is I really DO need a coolant temperature gauge. Whilst they're undoubtedly very useful I don't want to go down the 'OBD display' route 
I just want a plain and simple coolant temp gauge and I'm fortunate to have one sat in the workshop just waiting to be fitted. Nothing flashy just an LED display, a few wires and a sender unit. The sender having a 'standard' 1 1/8" NPT thread. This is where the challenge lays, as a quick look around the engine bay yields no obvious place to fit the sender, the OE VAG item being a push fit into a plastic housing. No sturdy aluminium inlet manifold or thermostat housing to drill and tap. The easiest option I can see being to fit an adaptor into the top hose. I realise that this is not ideal as this isn't really monitoring the engines actual true coolant temperature, and will not really be of any use until (and unless!!) the thermostat opens, but it may have to do? ...better than nothing I'm thinking. I hoped someone has found a better solution. Somewhere suitable to drill and tap a thread?? or??
sounds like an idea. Would you happen to know if the circuit is 5v or 12v ...or? I had assumed (maybe wrongly?) it to be 5v and a mismatch with my gauge and hence not suitable. If I have time tomorrow I shall monitor the existing circuits voltage and see if that'll work. It'd be a great and simple solution. Though I am keen to keep all the wiring, particularly any 'signal' wiring separate from the vehicles existing wiring... not wanting to cause strange back-feeds and weird faults. So still in hope of someone else having done this