MG Car Repair: Electrickery, bad earth, brown wires

Question
Hello (again).



I'm having some serious electrical mayhem in my 73 Midget (US, I think).  When my headlights work, my brake lights don't.  Occasionally my turn signals don't work either.  My tail lights work on occasion, but not when the headlights are on.

I have power everywhere, and I've checked and cleaned all the grounds.  Things randomly decide to operate when I change from high beam to low beam.  

I really am very confused about this.  I tried a new light switch (out of desperation) and found the same results.

Feels like Lucas is beating the crap of out me.

I'm tempted to hire an electrician to rewire the entire car at this point.  Any advice you could give me?

Thanks,

David

Answer
Hi David.  This is a really tricky problem.  It seems that there is a limit to the amount of current the system can generate.  When you use the headlamps, they drain it, killing other circuits.  Apparently haphazard faults such as this are usually a bad earth somewhere.  I would start by removing the big earth strap from the battery and the other end attached to the car frame, cleaning everything, and then putting it back together.  

The other main problem area is usually the bullet connectors for the wiring circuit, especially the one under the dashboard near the ignition switch.  Look for a bunch of thick BROWN wires going into a 4-way connector.  Best to do this with the battery earth strap disconnected, because these wires are always live.  Pull the bullet connectors and inspect the black plastic coated terminal block.  You may need a new one.

Let me know how you get on.