MG Car Repair: 1975 MGB battery hookup, mgb roadster, starter solenoid

Question
I took the battery out of my 1975 MGB roadster over the winter.  I am new to British cars and I am not sure how to hook the battery back up.  There are black and blue battery cables and I assumed the black was negative, but when I tried to hook the black cable to the negative terminal (after hooking the blue to the positive) I got an unusual amount of sparks.  My question is if the cables should be hooked up in reverse of what I had previously done.

Answer
Hi Westyn,

The color of the cables does not mean anything. The cables most likely have been changed more then once and any color cables could have been installed. MG never had a blue cable. Most were black on positive and negative originally.

Your 75 MGB must have the negative post grounded. All British cars with alternators have negative grounds.

It is possible to damage the diodes in the alternator by connecting the battery backwards. Here is a rough method to find out if you damaged the diodes.

Connect the negative post of the battery (-) to the ground cable that is connected to the body of the car and then just scratch the positive cable (the cable that runs up to the starter solenoid) across the positive post of the battery. If everything is turned off you should not get any sparks. If not you can connect the cable. Put a volt meter across the battery post and read battery voltage (12.5+) and start the engine and set the RPM to a fast idle (about 1500 RPM) and read the battery voltage again at 1500 RPM and it should read 13.8v to 14.5v. If it does you have not damaged anything in the alternator.

Howard