MG Car Repair: Starter Wires, ballast resistor, mgb

Question
Hi Barrie, I have been making some real progress bringing my 79 MGB back to life after sitting for many years, and your help has been great.  Lately, I noticed when starting, the engine turns over very slowly (Fairly new battery).  After some online research I decided to double check some connections.  The ground strap on the battery was very rusted and corroded on the bolt area where it connects to the frame.  I will take care of that.  My question is, when I was cleaning the wires and connections to the starter I noticed a wire which wasn't connected.  It is the White/light green wire.  I see where there is a place to connect it, but I'm wondering if I should.  I am the original owner and have never disconnected it.  Would someone (mechanic) who has worked on my car possibly disconnected it in the past for some reason?  Is it important?  Should it be connected?  Thought I would ask you before I did something to screw up my electrical system. Also, any other suggestions to check with the slow starting, the engine turns very slow when attempting to start.  Thanks, Ernie

Answer
Hi Ernie.  The White/Green wire is the bypass for the ballast resistor.  Perhaps a mechanic replaced the starter or cleaned the solenoid?  Or the wire could have corroded and snapped.  
If this wire is disconnected, then the coil will not produce the maximum spark whilst you are trying to start the engine, so the car will be hard to start.  Once the engine is running, this wire does nothing, it is only an aid to starting.
 
By the way, check the earth wire connecting the gearbox to the frame of the car.  It is usually bolted across one of the gearbox mounting rubbers.  This is just as important as the battery earth strap.