P.J. Hartman: The side marker lights are not wired in series on the
MGB. Replacing the bulb in the front light will not make the rear
lamp light. Sorry. You might also want to have a good look at the
ground (-) for the rear lights. I belive it is in the vicinity
of the boot latch. Note that the same attachment point carries
the ground (earth) for the fool pump.
Mike Passaretti: From Bill Piggott's book, "Original Triumph TR"
...although the TR4 and almost all TR4A's were fitted with dynamos,
an altenator was offered as an option on the TR4A. It is uncertain
how many cars were delivered so equipped. Not that any of that helps
you. My '67 TR4A has an altenator on it. Certainly a PO job. Most of
the wiring harness has been melted! Anyway, the altenator is a
"Motorola Automotive" and I can't give you model numbers 'cause that
part of the altenator has been rubbing against the engine block for
years. It is about the same diameter as a Lucas, but, stubbier
(shorter?). Puts out about 45 amps at 2500 rpm.The heavy brown/
yellow wire goes to the input of the voltage regulator, which
would suggest that there is no voltage regulator in the altenator.
Indeed, I saw only Zenor diodes in it last week when I had it off
the car. It is hung on the side of the engine under the carbs
(unlike the six cylinder installation), and is shorter than a
dynamo to prevent it from fouling on the exhaust header. The
installation uses most of the existing dynamo mounting hardware,
the top bracket is drilled with one 5/16 hole and does not
permit any adjusting of belt tension. The altenator mounting
tabs are almost 180 degrees apart as opposed to the Lucas
unit which has the tabs at closer to ninety degrees. A few
years back, on a six hour drive into dark and rain, of three
TR4A's, mine was the only one able to restart after a short
rest stop. Seems the dynamos on the other two could not keep
up with the demand of the lamps and wipers. But, that is another
story.
Alan
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