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 | ||
| + | |- | ||
| + | |Headlight switch||30||Radio (constant)||10 | ||
| + | |- | ||
| + | |Coil||30||Wipers||15 | ||
| + | |- | ||
| + | |Door lock||20||Radio (switched)||10 | ||
| + | |- | ||
| + | |Cigarette lighter||20||Backup/cruise control||10 | ||
| + | |- | ||
| + | | Horn||20||Gauges||10 | ||
| + | |- | ||
| + | |Brake switch||20||Dome/Trunk light||10 | ||
| + | |- | ||
| + | |Power windows||20|| Power antenna||10 | ||
| + | |- | ||
| + | |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. | ||
| + | ===Testing a brake switch, etc.=== | ||
| + | *Set the meter to the 20 VDC volt scale (or whatever is close to that). | ||
| + | *Ground the negative meter lead, then probe the wires separately. In the "at rest" position- brakes [B]not[/B] depressed- there should be power IN but not OUT. | ||
| + | *With the brakes depressed there should be power at BOTH terminals. | ||
| + | **If there is no power IN, the wire has burned or the fuse blown, or the wire has been disconnected. | ||
| + | **If there's power IN to the switch but nothing OUT with the switch activated, you have a bad switch. | ||
| + | *You can also test the switch using the ohm setting, be sure to disconnect the switch from the wiring first. Connect the meter leads, one lead to each terminal. If the switch is OK, you should have continuity (close to zero) with the switch activated (brakes ON), and infinity with the switch at rest. | ||
| + | **If you have a high ohm reading w/the brakes ON, or infinity, the switch is no good. | ||
==Miscellaneous== | ==Miscellaneous== | ||
| + | One must realize that many times you will supply power to a circuit (i.e. tail lights), and other times you will supply a ground, as the circuit have power supplied directly to them, and the ground is what is switched. This is very common in courtesy lights that are grounded when the door switch is activated. | ||
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| + | Sometimes you must use existing wires (as when they go from the dash, up the A-pillar, across the top, to a courtesy (interior) light. These are seldom removable if you have the headliner in place. Use a test device to be sure there are no shorts or 'opens' (broken wires). | ||
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| + | If you are changing from 6 to 12 volts (a very good idea), your new wire does not have to be as large as the original, as the current will only be 1/2 the original. This can be important when buying wire in several colors. You can often do much of the wiring using 14ga wire, or even 16ga, but be sure to determine the current draw before committing to a particular gauge of wire. Also, if you use LED lights, the current is minscule! And, they generate no heat to speak of. | ||
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| + | Sometimes a custom harness will be cheaper, especially if you want to use factory color codes. | ||
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Furthermore, it is suggested that a maxi fuse is installed rather than a fusible link. A lot of this is personal preference. However, it is too easy to pop a new maxi back into the socket and avoid the REAL problem -- what took it out? A fuse link MUST be cut, repaired, soldered and heat-shrunk back into place to be repaired. This will motivate you to look into WHY it went out. | Furthermore, it is suggested that a maxi fuse is installed rather than a fusible link. A lot of this is personal preference. However, it is too easy to pop a new maxi back into the socket and avoid the REAL problem -- what took it out? A fuse link MUST be cut, repaired, soldered and heat-shrunk back into place to be repaired. This will motivate you to look into WHY it went out. | ||
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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 starter. | 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 starter. | ||
| − | + | [[Category:Ignition]] | |
[[Category:Electrical]] | [[Category:Electrical]] | ||
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