Rewiring a vehicle

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! Accessory  !! Amp!!Accessory!!Amp  
 
! Accessory  !! Amp!!Accessory!!Amp  
 
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|Headlight switch||30||Radio (constant)||10
 
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|Coil||30||Wipers||15
 
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|Door lock||20||Radio (switched)||10
 
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|Cigarette lighter||20||Backup/cruise control||10
 
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| Horn||20||Gauges||10 
 
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|Brake switch||20||Dome/Trunk light||10
 
 
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|Power windows||20|| Power antenna||10  
 
|Power windows||20|| Power antenna||10  
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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.===
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*Set the meter to the 20 VDC volt scale (or whatever is close to that).
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*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.
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*With the brakes depressed there should be power at BOTH terminals.
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**If there is no power IN, the wire has burned or the fuse blown, or the wire has been disconnected.
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**If there's power IN to the switch but nothing OUT with the switch activated, you have a bad switch.
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*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.
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**If you have a high ohm reading w/the brakes ON, or infinity, the switch is no good.
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==Miscellaneous==
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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.
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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 starter.
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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 start
 
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[[Category:Ignition]]
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[[Category:Electrical]]
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Latest revision as of 06:10, 30 December 2024

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