Posted on: March 27, 2009

by Nick O’Dell in the September 1994 RootesReview

If you`re a purist, someone who would be outraged to see radial tires on a Mark 1 Alpine, for instance, read no further because what follows will probably curve your spine. However, if you’re of a more practical mind, this is how I permanently fixed “The Curse of Joe Lucas” with my Mark V.

Electrics were the Achilles heel of English cars until recently, and Sunbeams were not immune. After replacing the Lucas alternator and control box (twice each) and the relay, I had had enough. I found that a standard AC Delco alternator, with a small amount machined from the base to fit the Alpine mounting bracket, will bolt in place and use the stock fan belt.

The beauty of this unit is threefold:

1) it’s cheap and easily replaced;

2) with 60 amps on tap you will never run out of juice to run auxiliary lamps etc.;

3) the built-in regulator eliminates the troublesome external control box and relay.

Wiring is simple. There are three terminals:

Main Output terminal is the equivalent of “B+” on the Lucas unit;

Sensor, which monitors battery voltage and thus controls alternator output, connects to the battery connection at the starter solenoid;

Field, which energizes the alternator when ignition is switched on, connects to terminal #1 on the ignition switch.

That’s it, right? Nope. You would repeat my experience: the charging system working fine but with the interesting phenomenon of the engine continuing to run with the ignition switched off and the key in your pocket. Reverse voltage feeds back from the alternator and energizes the ignition coil. This is eliminated by splicing an in-line diode (e.g. Radio Shack part# 276-1141) into the Field lead, allowing voltage only from the ignition switch to the alternator, not in reverse. The diode will only work one way: if the engine continues to run, reverse the diode.

This conversion may also work with earlier (generator) Alpines, bringing all the benefits of an alternator. I did mine when I completed my Alpine restoration in 1980 and it has run faultlessly ever since, a perfect marriage of classic English and “know-how” American. It will horrify the purists, but boy! it works.

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