GM Alternator Conversion

Lucas alternators are perfectly suited for the needs of the MG Midget when it rolled off of the assembly line. However, if you have ever been 200 miles away from home and one dies on you, you can guess the frustration in trying to get a replacement over the counter at your neighborhood Kragen/Pep Boys, etc.

Also, if you want to run higher powered accessories like hallogen headlamps, and modern stereos, a higher output alternator is very desireable.

Most common is your basic "GM One Wire" alternator. The drawback to this conversion. is that the good old standby GM alternator only has two mounting ears. When bolted to the fragile waterpump of an A-series Spridget engine, the stress presented by proper belt tension will break the mounting ear off of the water pump.

The GM alternator I went with is a newer design. It is from a late 80's 3.1 Liter V-6 Corsica. It has three mounting ears, and they are in similar position to the ones on the Lucas alternator. It has provisions for sensing both load and battery charge levels, and also works with the charge warning light circuit.

A new adjusting bracket must be fabricated. I went to the local wrecking yard and found a bracket from a late-eighties Ford Ranger. I shortened the bracket, and ground it down slightly to clear the alternator cooling fan.

Wiring of the alternator is very simple. You will need the GM plug that matches the alternator. There are four wires on this plug, but only two of them are utilized. The plug terminals are labeled S,F,L,P.

S=Red wire, splice to the smaller gauge brown wire. This circuit senses the battery load.

F=Not used, cut off at plug

L=Brown wire, splice to the brown w/yellow tracer wire. This is the indicator circuit.

P=Not used, cut off at plug

Attatch an eyelet connector to the Large Brown wire and connect this to the post on the back of the alternator marked "BAT". This is the supply wire from the alternator.

When wiring the system, keep in mind safety, and servicability.

Please note that I am not a professional mechanic, electrician, or engineer. Before attempting any alteration on your car consult with a qualified technician.