GM starter wired to alternator

GMC guy

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#1
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MAKE: Pontiac
MODEL: Trans am
YEAR
: 1980
MILES: 100,000
ENGINE
: 350
DESCRIBE ISSUE....Guy brought this car to me. Electrical problems off all variety. The starter is wired to the alternator. and there are several patched wires running from that connection. Guy heard a pop under the hood. The car stopped charging, but has suddenly begun charging again. I'm kinda sure I never saw a starter connected to an alternator....but I have to ask...is this the way they are wired?
 

EricC

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#2
This diagram is from an '82 Camaro, but I remember them being similar from that era. With regards to your problem, I'd start by gently pulling wires looking for a burned fusible link.
 

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kev2

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#3
simply put -the alternator charge wire would go to meet the pos battery cable at the starter lug... and as mentioned fusible links!!

a quality 1980 diagram will be tough to get esp for a trans am-- sure its a 5.7L ? but we can do if needed.
 

GMC guy

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simply put -the alternator charge wire would go to meet the pos battery cable at the starter lug... and as mentioned fusible links!!

a quality 1980 diagram will be tough to get esp for a trans am-- sure its a 5.7L ? but we can do if needed.
Yeah it's a 5.7. The guy transplanted this from the original engine. Original was smaller but not sure which engine it was. But the wiring job is terrible.
 

Gus

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#7
Every GM car that I know, is wired this way......Main battery feed goes to the starter solenoid....off the same connection, a wire goes to the alternator through a fusible link....that is the large red wire attached to the alternator usually with a nut......
 

GMC guy

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Every GM car that I know, is wired this way......Main battery feed goes to the starter solenoid....off the same connection, a wire goes to the alternator through a fusible link....that is the large red wire attached to the alternator usually with a nut......
Ok thanks. The wire from starter is same size as battery cable and not fused, therefore causing shorts as there is no fusible link to protect alternator
 

nickb2

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#10
At least you had the sense to know this was all wrong. Sometimes fuse links are hard to come by, but I always fuse my wiring and use proper gauge wiring. If not, always a space for a fire.

I think I told this story once here, but a buddy of mine bought a jaguar with a chevy 350 conversion. That car lit up big time. Stupid mistake.

I see this crap almost everyday.

 
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#11
Alternators are current limited, don't need fusible links, typical is a 10 awg wire from the B+ terminal directly to the positive terminal of the battery. Should be a 4 AWG wire directly to the starter terminal solenoid like Gus said. Has peak currents in excess of a 1,000 amperes, if connect to the alternator B+, kind of dumb trying to get that much current through a 10 AWG wire.

Yeah, they kind of like to use that starter terminal as a point to get 12V way back to the body connector that feeds the main fuse box for everything else. Starter was about a mile back from the battery, did that, also subject to corrosion. P 30 was this way when the body connector was only six inches away from the battery. Changed that and had a very long piece of 10 AWG wire left over for more important uses.

Wiring on these older vehicles was very basic, can really go nuts on todays vehicles.