MG Car Repair: MGB wiring question, left turn signal, voltage stabilizer

Question
Hi Barrie - trying to identify a strange wire on my 74 1\2 MGB (US). It is a red wire ( outer insulated, inner red rubber jacket w\ solid alum core ,not braided copper and insulation looks like it maybe sustained heat damage )It pops out of harness near fuse box area..hanging in air - runs toward lights and surfaces from harness near left turn signal, and connects to a White\green stripe wire in connector. I cannot see on wiring diagram or tell where w\g\ wire goes.. Testing this connection, w\ key "on" it shows .01V, and w\ engine running is 12.2V. All electrics are working, but engine runs hot. any ideas? thanks! P

Answer
Hi Paul.

The strange red wire that you describe is shown on the wiring diagram as a zig-zag.  It is the resistive wire providing power to the coil while the engine is running.  Your car has an 8 volt coil and this resistive wire drops the supply from 12 to 8 volts.  This wire is bypassed while the starter is in operation.  It is made from a strange metal that cannot be soldered, so at each end there is a crimp terminal hidden inside the wiring loom.  The wire where it surfaces is probably White with a LIGHT Green stripe (WLG).  They look very similar.  It connects to the + terminal on the coil.  At the other end it may be connected to either White (W) or White with Brown (WN)wires depending on whether your car is a 74 or a 75.  

I don't think this wire has any connection with your engine appearing to run hot.  I would start by checking the temperature gauge.  In particular, 1974/5 USA cars had an electrical temperature gauge that was powered via a voltage stabilizer which also supplies the fuel gauge.  If the fuel gauge is also reading high, then the voltage stabilizer has failed and needs to be replaced.  Or possibly you have a faulty thermostat or a badly corroded radiator.  Or maybe the ignition timing is retarded too much.  Let me know what you find.