Alternator not charging,A/C compressor power unidentifiable

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Amanandhistruck

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Joined
May 27, 2020
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Location
Florida
First Name
Michael
Truck Year
1987
Truck Model
k15
Engine Size
350
Evening y'all,so I've read the schematics,and I've read the pages on the differences between the 1 wire and 3 wire alternator,but none are for my year. I have a 1987 V1500 with a 4 wire shown below. I've wired the small red wire straight to the battery from the nut,wired the S voltage sense wire to the nut,and the key power to the brown wire leading back to the original harness. Both the F and P wires are unused. I have not tested the alternator itself at the parts store,but its supposed to have "low hours". While driving voltage doesn't exceed 11.8V regardless of RPMs. Did I wire it correctly? There is a fusible link in the same wire loom as the brown wire,and it sparks when I touch a hot lead,is it supposed to be wired to the alternator as well? Additionally,I cannot find the green power wire for the A/C compressor. Where on the firewall,or which loom would it most likely be? Thanks in advance for any input.
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eskimomann209

Full Access Member
Joined
Jan 9, 2019
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1,998
Location
Modesto
First Name
Marcus
Truck Year
1973
Truck Model
C10
Engine Size
5.3
That wire off the alternator looks a little anemic to me. Also the wire you’re calling brown with the fuse, I believe it’s actually a faded red wire.
under that link it looks nice and red, so yeah I’d say it needs power. And probably needs attaching to the alt. Looks too short to go anywhere else. while the truck is running check voltage ( with a voltmeter) off the lug on the back of the alternator. Then check the voltage at the battery and compare those two. If the read 14ish than your gauge is incorrect. That’s not uncommon. If it’s not at 14. Something ain’t right be it a ground, wire sizing, or that plug.
 

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