Alternator wire question
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Trailering
Joined: Mar 2025
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Alternator wire question
I have looked at several wiring diagrams and cannot find out where a larger gauge black wire with a pink ( lavender) stripe is supposed to connect. One end connects to the top right post on the alternator and the other end has a larger round connection loop on it. Any thoughts on where this loop is supposed to connect? Thanks very much.
Logistics Pro
Joined: May 2015
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From: Tri Cities, TN
I believe if you look closely at the terminal on the ALT. it may be marked GND, that wire is a ground. It should be bolted to the engine; it is also paired with a smaller wire of the same color that grounds at the voltage regulator.
Logistics Pro
Joined: May 2015
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From: Tri Cities, TN
You need to get your multi-meter out and check continuity on that because the ground is Black/Red stripe it has three places it connects, the ALT, the Engine and the Voltage regulator. The only solid white wire on the ALT is the Field wire.
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Trailering
Joined: Mar 2025
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Crop Duster, There is a black and yellow double wire that runs between the alternator and voltage regulator in the original wire harness that ends about a foot before it reaches the alternator. Any thoughts on where this hooks to? Thanks again and I will try not to bother you again.
Logistics Pro
Joined: May 2015
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From: Tri Cities, TN
The black/yellow stripe is the BAT wire. It runs from the ALT battery terminal to the battery side of the start relay. The solid yellow wire paired with it goes to the A terminal on the voltage regulator. The wiring for the alternator is an important circuit if you get it wrong it won't charge or could burn up all the wiring in your truck.
Have you considered buying a new ALT harness they aren't expensive and might save you from an electrical disaster. NEW! Voltage Regulator Alternator to Wiring Harness V8 1965-1966 Ford F100 Truck | eBay
Have you considered buying a new ALT harness they aren't expensive and might save you from an electrical disaster. NEW! Voltage Regulator Alternator to Wiring Harness V8 1965-1966 Ford F100 Truck | eBay
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Trailering
Joined: Mar 2025
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The wiring harness is not in bad shape, the truck sat idle for 40 years. When I installed the new alternator I matched the wires up as they were on the original one, same thing for the new voltage regulator. The wires in question are a solid black one and a solid yellow one and fused together to a 3/8 inch wire loop and run in the wire harness and stop about a foot from the alternator. There is no way to reach anything but the block. The engine is a six cylinder. Thanks for your patience.
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Logistics Pro
Joined: May 2015
Posts: 4,474
Likes: 974
From: Tri Cities, TN
The battery wire that is paired with the yellow wire is about 2 ft long so it should easily reach from the Alt. to the start relay the loop where they are paired together goes on the start relay and since the harness has a plug for the regulator you can't put it in backwards. Are you certain you have the correct harness, and have it routed correctly?
I my opinion any under hood harness that is 60 years old is not in good shape.
I my opinion any under hood harness that is 60 years old is not in good shape.
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Trailering
Joined: Mar 2025
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Completely disregard my last post, I opened up the harness and found the larger black wire comes from the alternator and the smaller yellow wire joining it goes to the regulator. I these should connect to the battery side of the starter relay. Thanks.
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