Help Please - Electrical fire!

[BoSelecta]

hi all - after queuing nose to tail for 2 hours for the blackwall tunnel this afternoon the car had enough and I saw smoke coming from the bonnet. Opened up to see a cable tie aflame which as taken a couple of wires with it...I managed to drive home 15 miles from there with no obvious symptoms but needless top say im worried. Especially as I'm moving house tomorrow. Can anyone let me know what these wires are? Thanks...

[BoSelecta]

I've deduced that the wire which has burnt through completely is likely an earth from the carb to the head. The other 2 I cant figure out - I realise that it's nigh-on impossible for someone to see what's what in these pictures. Are there any wires in the mk2 which would be terminal for the engine/safety if compromised? I was under the impression everything is pretty much mechanical - only think i can think would possibly be alternator to battery but this is likely quite a thick wire yeah? All of the HT leads to the plugs are fine...

[clipperjay]

More than likely ignition or coil wires I would simply trace and replace with same gauge wire! 
Hard to say but any earths that look oxidized I would replace aswell.
Trouble with this it could have been overheating somewhere as you would expect a fuse to have shorted unless a numpty stuck in higher rated fuses that caused the fire in the first place?
Check fuses to make sure they are the right ones in there!
 

[Santiago]

The other two wires are likely to be for the bypass heater on the front of the carb (the one with the inline connector), and the thermoswitch that's a little above that. I guess your car is CE2 electrics, 1990 or later? The feed to the bypass heater used to be fused on CE1 cars, but isn't on CE2, it's direct from ignition live. As you've found out, this wasn't a particularly great idea from VW.
The thermoswitch turns on the rad fan if the carb gets too toasty after shutdown on a hot day.  Helps prevent fuel evaporation from the float bowl, but at the cost of battery power. Not essential unless you really care about environmental stuff.

[clipperjay]

One thing check if there is a strong fuel smell around that carb seal its possible the float is sticking and overflowing the carb and seeping through the seal and down the pre heater manifold right under where those wires are sitting above like I said It could have been some fuel igniting and making those wires melt? Either way I think you were lucky this time!

[BoSelecta]

The other two wires are likely to be for the bypass heater on the front of the carb (the one with the inline connector), and the thermoswitch that's a little above that. I guess your car is CE2 electrics, 1990 or later? The feed to the bypass heater used to be fused on CE1 cars, but isn't on CE2, it's direct from ignition live. As you've found out, this wasn't a particularly great idea from VW.
The thermoswitch turns on the rad fan if the carb gets too toasty after shutdown on a hot day.  Helps prevent fuel evaporation from the float bowl, but at the cost of battery power. Not essential unless you really care about environmental stuff.

Do either of these heat the fuel mix in the carb to help with ignition? Had the car started up and round the block a few times and she starts very lumpy and with quite some help from the starter motor...Once up to temp drives like normal.

[Santiago]

Well the bypass heater warms the fuel/air emulsion on its way to the idle/progression outlet, but it won't affect starting, it couldn't get hot fast enough even if it was working. 

You've made sure that nothing is shorting any more? 

Maybe just a low state of charge in the battery due to the shorting/cooking?