Sunday while resurrecting my MGB ('74) from the operating table, I think I
managed to fry my alternator. The alternator that is in there does
not match up with the wiring diagrams in any of my books (Bentley,
Haynes, Clymer). It has four slots to hook wires that looke like this:
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I have three wires to hook to these slots, two brown and one brown
yellow. Being a wanker I did not properly diagram the way they were
before I took the alternator out, only writing a note that said
"Brown, Brown-yellow, Big Brown". When I went to hook it up I tried
to put the big-brown wire on the higher thick horizontal tab. This
was greeted with a shower of sparks and some smoke (I never did
unhook the battery. ooops). Since there wasn't much smoke and the
wire wasn't hot, I thought maybe I hadn't done much damage, so I
hooked the big brown wire to the lower thick horizontal tab and there
were no sparks.
I went on to get the car running and drive it for a while with no
problems, but I did notice that the headlights did not get brighter by
revving the engine like they always used to , so I suspect I fryed the
alternator. What is the proper way for the alternator to be hooked
up? I have a spare the only has three tabs, all horizontal, one thin
and two thick. (After removing a bunch of tape I did discover that
the smaller brown wire has a thick female tab the has had a thin
female tab taped to it, so I am guessing that the Brown/yellow wire
goes on the thin tab and the two brown wires go on the thick tabs:
-- (brown/yellow)
---- (brown)
---- (big brown)
Is this correct? There is also a screw for what looks like a ground
wire on the replacement alternator, but not on the alternator I may
have fried. So experts, how is this supposed to be wired? I want to
test the alternator that is in the car before doing anything, I
suppose I could just test the voltage at the battery to see if it goes
up as I rev the engine as I'd rather not stick a probe into the wiring
by the alternator so I can avoid another shower of sparks.
Thanks,
Bob
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