Lucas Electrics–I

The Sunbeam’s electrical system is very simple and in fact is has only two fused circuits. Still there seems to be much that can go wrong. Cousin Robert, owner of 1 1/2 Alpines back in the day, and more recently a Triumph TR6 that he restored to a treasure, warned me about Lucas, the prince of darkness.

The car arrived with a dead battery, not surprising since it had been stored for about a year. The battery took a charge, but after a few weeks, it was fully discharged again. After third time and with the engine actually running, I became suspicious that there was something going on. I tested the battery voltage with the engine (barely) running and found only 12 volts. A working alternator puts out 14 volts, so we had a problem. Gail, my wonderful daughter-in-law and the supervisor for the weekend, confirmed the results.

The problem could have been a bad alternator or bad voltage regulator. Lucas alternators of the era needed an external control to cycle electrical generation on and off, depending on the voltage. It turns out that a replacement for either would more expensive than a replacement alternator from a more modern car. According to Sunbeam experts, alternators from a mid 1970s Chevrolet or a 1980 Datsun truck would fit using the original Sunbeam bracket. Both were readily available at Advance Auto.

To make the alternator pulley align with the pulleys on the water pump and crankshaft, we needed to slide the bracket back along the engine block. Daniel cut slots in the bracket by drilling new holes and then cutting out the extra material. I went to the parts store for a new belt. Here is the alternator installed. The bolts that attach the bracket to the engine block are SAE fine thread. The adjustment bolt on the upper bracket that threads into the new alternator is metric. I found one in the parts bin from the 818.

The new alternator works perfectly.