Published on July 18th, 2012 | by Gearhead Diva0
How to Repair Automotive Electrical Wiring
Automotive electrical problems can be a pain in the butt. Do you try and tackle them yourself to save some money, or do you take it to a shop and forget about eating for a couple days to pay for it? Well, with the right tools, and the correct book for your car, they can actually be quite easy to repair. Below are some of the more common problems you can fix yourself.
Tools You’ll Need
- Electrical Repair Kit
- Basic multimeter
- Electrical tape or heat shrink tubing
- Repair manual for your car
The better auto repair manuals found at the large auto parts chains have wiring diagrams in the back. These diagrams can mean the difference between doing it yourself, and taking it to a shop, so I really recommend getting one.
Fixing Broken Solderless Connectors
This is the easiest type of repair there is.
1. Unplug and Cut Off the Old Connector
This type of connector comes in a variety of styles. How they’re unplugged depends on the type of connector. As an example, inline splices, also known as butt connectors, just get cut off on both sides of the connector. Terminals require removing the screw or bolt and then also get cut off. Spade lugs are just pulled off the male connector.
2. Strip the End
Many wire strippers are labeled by color indicating the size of the wire. Most car wiring is 16-gauge. Cut the end of the wire cleanly, and then place the wire with 3/4 inch of it sticking out of the stripper and grip it tightly with the stripper. Pull the wire out, removing 1/4 inch of the insulator. Twist the end of the wire.
3. Crimp the New Connector
Insert the stripped end of the wire into the connector until it bottoms out. Then, paying attention to connector color, place the connector about 1/8 of an inch from the wire end of the connector into the crimp jaws of the crimper and squeeze tightly. With inline splices, you’ll need to perform Steps 2 and 3 twice. Plug the fixed connector back in or reattach the ring terminal to the screw or bolt.
Fixing the Light that Won’t Come On
You’ve got a brake, tail, turn signal, or even a head light that won’t turn on. And you don’t know why. The problem could be a bad switch, bad bulb, or a broken wire. Here’s how to find out which problem it is, and fix it. You’re going to need that repair manual I mentioned above for this, because wire colors change from year to year and model to model.
1. Do the Swap Test
The name says it all. Put the bulb that’s not working into another socket/pigtail to test it. Make sure you hold the bulb glass with a tissue, napkin, or clean towel, as the acids in your fingers will eat the glass and cause premature bulb failure. If the problem bulb still doesn’t light up then it’s time to replace it. If the bulb does light up, continue with the steps below.
2. Probe the Wires for Power
First, find the black wire, which is (almost) always ground, and probe it with a continuity tester. Clamp the alligator clip to a good ground, and probe the back of the socket where the black wire goes in. If the bulb in the tester lights up, you’ve got a good ground. If not, trace the wire to where it’s broken and use the procedure above to fix it.
If the ground is good, use the other tester to see if the bulb socket/pigtail is receiving power. Use a large test light, or a multimeter set to test 12 VDC, and attach the clip to ground/firmly touch the black lead to ground. With either the probe end, or the red lead, first probe the back of the socket where the power leads go in. If you get power, you need to replace the socket using the procedure above. If not, you need to trace the wire until you find the break.
3. Check the Switch
If neither light is coming on, chances are you’ve got either a bad switch, or a wire broken from the back of the switch. The brake light switch is located on the pedal under the dash. Carefully disconnect it and use either the continuity tester or the meter set to test continuity, and probe the back of the switch. Then move the pedal as far as you can by hand. If the light doesn’t come on, or you hear no tone, you’ve got a bad switch.
If the switch is good, reconnect the connector and test both wires using the either the test light or the meter set to check 12 VDC. Press the brake pedal. If the light comes on, you’ve got a good switch and connection. If not, wiggle the wires, you may get lucky and just have to replace the connector.
4. Tracing the Broken Wire
For this step, you may need to remove interior trim panels and such. Normally, these are held in by either a screw or a locking push pin. Be careful removing the retaining device and panel. Next, using the book, locate the circuit you’re working on, and the wire that’s at fault. Usually, where the wire is routed will be at least hinted at in the schematics in the book. You may need to remove electrical tape to expose the wires. Typically, wires will break at junctions, connections, and splices. But, the insulator, being rubber, may look fine. So, when you locate a connection of any sort, wiggle it and have someone look at the lights. If they flicker, or come on, replace the connection.
Typically, if you use the sharp probe of the test light or continuity tester, you shouldn’t have to worry about the integrity of the wire or insulation. But, to be safe, wrap the wire at the point of the puncture with electrical tape. One wrap will be fine, that way the wire color can still be identified.