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Strange problem

Old Aug 23, 2008 | 07:37 PM
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Question Strange problem

I am just finishing up installing a new harness in my 75 F-250. I jumped in it the other night, and when i turned the key on the dash lights light up. When i turn on the headlights, my gauges start working. I am thinking i have a crossed wire somewhere, but i cant work on it for the next couple days, and it bugs me when i think about it. Anyone have any insight on this?
 
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Old Aug 23, 2008 | 11:27 PM
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If you don't find any crossed up wiring, then you need to make sure you have good grounding. The large battery neg wire probably goes to the engine block. The engine and tranny are mounted in rubber mounts, so you need to run a short piece of wire from the engine block to the firewall. You may also need to ground the frontend radiator support with a short piece from the battery neg to the sheetmetal. Don't forget the frame too, since the cab is mounted in rubber body mounts, so a wire bolted to the frame will ground it.
 
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Old Aug 24, 2008 | 02:57 AM
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I would do it a little differently. Mostly for looks.

Run a wire from the engine block to the frame (or body) and from this same spot run a wire up to the battery. You will need to use a wire at least as large as the biggest you currently have or plan to use. Personally I wouldn't use less than 4ga, you can probably pick up 4ga welding wire from your local hardware store. Welding wire is typically high strand count so it's flexible and carries plenty of current. Also make sure your alternator to block surfaces are clean and can pass ground easily.

Without looking up a wiring diagram, but if your lights turn your gauges on then I would suspect a wire from that switch is connected to the wrong place on the cluster. Does anything else odd happen?
 
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Old Aug 24, 2008 | 08:35 PM
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i havent found anything else odd, but i am going to check the wires for my gauge cluster and the grounds. I am guessing i crossed some wires in the cluster. But once i am able i am going to run through everything again. I have had nothing but problems with this new harness. If any one can tell me how to wire up my dual tanks, it would be appreciated. That is another thing that was left out of the painless kit.
 
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Old Aug 24, 2008 | 10:47 PM
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Do you have a switch already?

I would think you could do this easily with a Double pole Double throw toggle switch. Basically it is two switches in one, on one side, the center would be connected to your fuel level gauge, and each of the outer pins would go to each of your sending units. The other side would I would use a ground on the center pin and run the pins toward the corresponding tank. These grounds would trip relays to power up the intank fuel pumps.
 
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Old Aug 25, 2008 | 12:07 PM
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Run a wire from the engine block to the frame (or body) and from this same spot run a wire up to the battery. You will need to use a wire at least as large as the biggest you currently have or plan to use. Personally I wouldn't use less than 4ga, you can probably pick up 4ga welding wire from your local hardware store. Welding wire is typically high strand count so it's flexible and carries plenty of current.
The factory usually did run the large battery neg to the frame and the engine block with one special wire, but you should not need this size wire on the body. If you will never put any thing large on the rear of the truck(such as a lift gate or winch) and will not be using the frame as a ground for one of these type of loads, you really don't need that large of a ground on the frame either.

As long as you keep in mind what your loads are, the starter is really the only amp hungry monster on the truck that needs the 6 or 4 gauge wiring. Of course if you want to run this large wiring for all your grounds, it will not hurt anything but your pocket book.
 
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