Like most LBC owners, I was always wondering if the battery would be charged and watched in apprehension as the head lights dimmed as I came to a stop sign. When I heard that I could replace my Lucas alternator with a Bosch unit I immediately headed for my local parts store.
I originally converted to this alternator in the mid 1990s. At that time Ford Fiestas were plentiful both on the road and in the junkyard. In 2006 the situation is significantly different; nearly all Fiestas are off the road. As a result the alternator is a special order from all of the major part stores. This is only a problem when your alternator breaks down in the middle of nowhere (where all breakdowns occur).
If you are still game, request the optional high amp Bosch alternator for a 1978 to 1980 Ford Fiesta with A/C & rear window defrost. The standard Fiesta alternator is a Motorcraft so be sure to ask for the Bosch. This particular alternator was also used in the 1976 VW Rabbit. The large brown wire attaches to the B+ terminal on the alternator, the small brown/yellow stripe wire attaches to the D+ terminal on the alternator and the remaining wire should be tied back and isolated (insulated) from ground. These Bosch alternators bolt right up and plug directly into the existing TR6 harness. The adjusting bolt thread on the Bosch alternator is metric so be careful not to damage the thread with an SAE bolt. Various reference numbers that have been supplied for the Bosch are as follows: 120 489 244, D8RZ-10346-AX, AL 119X, NAPA AL86X BSH, AutoZone 131071.
The following belt info applies to a Bosch alternator being installed into a 1974 TR6 and will probably apply to other years as well. For best results, use a 45" belt (Kelly Springfield 17450). The stock belt which measures 44 1/2" fits but the alternator will be located at the beginning of the adjustment slot restricting access to the #1 plug. A 45 1/2" belt locates the alternator near the end of the adjustment slot.