Rewiring a vehicle
From Crankshaft Coalition Wiki
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| + | ==Overview== | ||
When completely rewiring a vehicle there are a few things that must be determined beforehand. First, one must decide if a prefabricated harness will be used, or if a custom harness will be made from scratch. In any case, the harness should be assembled into groups and cut within a reasonable distance to the right length, while leaving extra wire to account for routing. | When completely rewiring a vehicle there are a few things that must be determined beforehand. First, one must decide if a prefabricated harness will be used, or if a custom harness will be made from scratch. In any case, the harness should be assembled into groups and cut within a reasonable distance to the right length, while leaving extra wire to account for routing. | ||
==Scratch-built harness== | ==Scratch-built harness== | ||
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If you intend to scratch-build your harness, will need a few things from the garage: | If you intend to scratch-build your harness, will need a few things from the garage: | ||
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*Accurate wiring diagrams, as well as YOUR notes and drawings made for the new system to be installed. | *Accurate wiring diagrams, as well as YOUR notes and drawings made for the new system to be installed. | ||
| − | If soldering: | + | ===If soldering:=== |
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*Good soldering station (don't use an undersized or non-controlled unit; it will slow things down) | *Good soldering station (don't use an undersized or non-controlled unit; it will slow things down) | ||
*Solder (24 gauge 60/40 is good) | *Solder (24 gauge 60/40 is good) | ||
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#Locate all your remote ground areas, such as headlight and tail light buckets, fuel sender/tank grounds, and any local grounding areas. Clean and burnish all paint, dirt, and grease from these areas, install a proper ground, using a star washer, lock washer, tech or sheetmetal screw. | #Locate all your remote ground areas, such as headlight and tail light buckets, fuel sender/tank grounds, and any local grounding areas. Clean and burnish all paint, dirt, and grease from these areas, install a proper ground, using a star washer, lock washer, tech or sheetmetal screw. | ||
| − | + | ===Build and install the ground buss system:=== | |
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#Run a proper-gauge ground cable (4 gauge or better) from the battery to any handy bolt at or near the starter. From that same bolt, get a battery cable at the parts store that has two 3/8" ring terminals on each end and attach it there and to the frame, following the shortest run possible. | #Run a proper-gauge ground cable (4 gauge or better) from the battery to any handy bolt at or near the starter. From that same bolt, get a battery cable at the parts store that has two 3/8" ring terminals on each end and attach it there and to the frame, following the shortest run possible. | ||
#Next, get some 10 gauge wire and ring terminals, and run that from your bolt on the block to the firewall, and another to the alternator bracket or mount bolt. | #Next, get some 10 gauge wire and ring terminals, and run that from your bolt on the block to the firewall, and another to the alternator bracket or mount bolt. | ||
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#Do the same for the whole diagram. You can get software to make your own schematic on your computer. This is where all your notes and line drawing will merge into a single easy-to-read schematic, which will be useful in the future. | #Do the same for the whole diagram. You can get software to make your own schematic on your computer. This is where all your notes and line drawing will merge into a single easy-to-read schematic, which will be useful in the future. | ||
#Next, one last time, ring or continuity check your harness point to point with an OHM meter or ring box. Make sure your connections are correct, and conducting, and conform to your line drawing (you can do both steps at the same time). Once you confirm all is correct, you can power test the system. | #Next, one last time, ring or continuity check your harness point to point with an OHM meter or ring box. Make sure your connections are correct, and conducting, and conform to your line drawing (you can do both steps at the same time). Once you confirm all is correct, you can power test the system. | ||
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| + | ==Fuse requirements== | ||
| + | For heavy draw accessories a [http://www.crankshaftcoalition.com/wiki/Relay_application_guide-_Bosch_relays '''relay'''] is the preferred method of wiring a circuit. Some things that can benefit from a relay: | ||
| + | *Headlights | ||
| + | *Cooling fans | ||
| + | *Fuel pump | ||
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| + | For circuits having a high draw a circuit breaker may be substituted for a large capacity fuse. | ||
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| + | ;Basic fuse requirements (from [[Media:Harness inst painless.pdf|Painless wiring]]): | ||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | ! Accessory !! Amp!!Accessory!!Amp | ||
| + | |- | ||
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| + | |Power windows||20|| Power antenna||10 | ||
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| + | |Turn signals||15||Electric fan relay||5 | ||
| + | |- | ||
| + | |Emergency flashers||15||AC/Heat relay||5 | ||
| + | |- | ||
| + | | Electric fuel Pump||15 | ||
| + | |} | ||
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| + | The fuse requirement and wire gauge has to take the accessory load into consideration. Using too small of a wire can let a wire burn even though the accessory load matches the fuse rating. Using too 'big' of a fuse can let a wire burn even if the wire gauge matches the load. | ||
==Testing== | ==Testing== | ||
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The first recommendation is a bench supply that has a current adjustment as well as an adjustable voltage control, is fused, and regulated. Not everybody will have one, or be able to afford one. Try borrowing one; it allows you to apply power with the current and voltage controls at zero. You can then adjust the voltage to 14.2, then slowly bring up the current. If you have a short, the AMP meter will shoot up rapidly, as you apply small amounts of current. In this manner you can turn the supply off LONG before ANY damage will occur, and correct the problem, AND if it exceeds the maximum draw for the supply, it will trip the fuse. | The first recommendation is a bench supply that has a current adjustment as well as an adjustable voltage control, is fused, and regulated. Not everybody will have one, or be able to afford one. Try borrowing one; it allows you to apply power with the current and voltage controls at zero. You can then adjust the voltage to 14.2, then slowly bring up the current. If you have a short, the AMP meter will shoot up rapidly, as you apply small amounts of current. In this manner you can turn the supply off LONG before ANY damage will occur, and correct the problem, AND if it exceeds the maximum draw for the supply, it will trip the fuse. | ||
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The second recommendation is a motorcycle battery (not a big Harley batter, a small hold-in-your-hand Honda-type battery). Install a 30 amp fuse link on the positive, and, (if your meter supports it) use your meter in line to monitor current. At this point you will be doing no "high current testing" so you should be good. If not a motorcycle battery, two parallel connected lantern batteries should last long enough to do some primary testing. | The second recommendation is a motorcycle battery (not a big Harley batter, a small hold-in-your-hand Honda-type battery). Install a 30 amp fuse link on the positive, and, (if your meter supports it) use your meter in line to monitor current. At this point you will be doing no "high current testing" so you should be good. If not a motorcycle battery, two parallel connected lantern batteries should last long enough to do some primary testing. | ||
| − | + | If you must use a battery charger, disconnect ANY electronics you have: CD player, tach, ECU, ECM, alternator, regulator, digital dash displays, and anything solid state to avoid damage. | |
Whatever system approach you take, test for functionality, correct any errors you may find. | Whatever system approach you take, test for functionality, correct any errors you may find. | ||
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Fuse links, unlike fuses, do not just blow -- something major is wrong! And, it was wrong long enough to melt wire -- unlike a 5 amp radio fuse that sees a 7-amp spike and opens a few times a year. It took a 50, 70 or 100 amp short of a few seconds/minutes to melt the link -- not a small issue. Find out why! | Fuse links, unlike fuses, do not just blow -- something major is wrong! And, it was wrong long enough to melt wire -- unlike a 5 amp radio fuse that sees a 7-amp spike and opens a few times a year. It took a 50, 70 or 100 amp short of a few seconds/minutes to melt the link -- not a small issue. Find out why! | ||
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In either case, a maxi and fuse link do the same job -- a 70-amp maxi is the same as a 70-amp link. What is important on either is to never install them inside a passenger compartment. They do their job by heating and melting, and can cause fires to interior parts, melt plastic parts, and create toxic fumes in a closed compartment. Always install them in the engine bay away from fuel, hydraulic, or other flammables. | In either case, a maxi and fuse link do the same job -- a 70-amp maxi is the same as a 70-amp link. What is important on either is to never install them inside a passenger compartment. They do their job by heating and melting, and can cause fires to interior parts, melt plastic parts, and create toxic fumes in a closed compartment. Always install them in the engine bay away from fuel, hydraulic, or other flammables. | ||
| − | While some wiring harnesses recommend the main power come off the starter live connection, running the wire straight to a single insulated battery terminal post can be a better way to go. Such a case would be an off-road vehicle where water or mud could cause problems if the main power wire is connected to the | + | While some wiring harnesses recommend the main power come off the starter live connection, running the wire straight to a single insulated battery terminal post can be a better way to go. Such a case would be an off-road vehicle where water or mud could cause problems if the main power wire is connected to the start |
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