For most car owners, the scope of electrical system knowledge stops at the fusebox. If it isn’t a bad fuse or bad bulb, that is as far as they can go into fixing the problem. The intrepid DIYer, however is not afraid of diving into an electrical problem, even though they may not have more experience or knowledge than the average person. If you have an electrical issue and want to solve it yourself, there are a few tools that can help you get it sorted, without having to attend a tradeschool on your nights and weekends.
These tools help you diagnose and repair common (and not so common) issues in your vehicle’s electrical system. No roadside tool box should be without them. All of these are available at your local auto parts store, in case you don’t already have them.
The main tool you need for diagnosing just about any electrical problem is the DVM or Digital Volt Meter. Most of these come with a dial knob, a readout and some test leads. At first glance, it is a really complicated tool that requires a degree from MIT to use, but in reality, it is not that tough.
The most common symbols on a DVM are Volts AC, Volts DC, Amps, Ohms, and sometimes continuity. If you can’t remember the symbols, a look at the scaling will help you out. Scaling varies by the manufacturer and model. Some DVMs are auto scaling, those are higher-end pro units.
Volts AC– This is noted by a V~, for alternating current. This is house current, you will not use this very often in a car. Typical scaling is 200v and 500v.
Volts DC– Likely the most often used setting for automotive work, DV volts is noted by V with a solid line over a dashed line. Scaling usually starts around 200 millivolts, 2, 20, 200, and 1000 volts. This is what you use to test power for just about every single component on a car. Most operations in a vehicle will use the 20v setting.
Amperage– Noted with an A and the same solid line over dashed line for DC current, amperage is typically scaled 200m, 20m, 2m, and 200m. Unless you know what you are doing, amperage testing should be done very carefully. You need to read the instructions for your meter, as many meters have a separate terminal plug for the higher-scale amps. Too much amperage running through your DVM can blow it up instantly.
Ohms– Also known as Impedance, the Ohms scale is noted by the Roman Omega, which looks like a fancy horseshoe. This setting is used for speakers, capacitors, and most helpful for testing sensors and ignition coils.
Continuity– This is a test that is used to determine whether a wire is broken, bad terminals, testing grounds, etc. It is very useful and the better meters have a tone that plays when continuity is detected. The symbol is a sideways triangle with a horizontal line running through it and a vertical line at the point, intersecting the horizontal line.
Test Leads– You will have 2 test leads, usually red and black. The red is positive, the black is negative. If you reverse the leads, you will get a (-) reading on your voltage tests. Not a big deal, but it might throw you off when you are under the dash of your car.
Get to know your DVM. Test your battery, alternator, and other components with the engine running and engine off. This will help you get familiar with how the meter works as well as how your vehicle’s electrical system functions.
There are three common hand tools that you will need for any electrical service work- cutters, crimpers, and strippers. You can buy one tool that does them all, but it won’t do any of them as well as separate tools will.
Cutters– You must have good, sharp cutters. Diagonal cutters, also known as side cutters or “dikes”, are the most common and most useful. Buy a full-size set that is large enough to handle most wire sizes, mini-cutters are not very good for larger wires. For battery cables and really big wire (4-gauge or bigger), a pair of hose cutters or garden cutters works really well.
Strippers– No, not the ones that leave you covered in glitter, these are the useful kind of strippers. There are two kinds of strippers- manual and automatic. The automatic strippers lock the wire in the jaws, cut and pull the insulation off of the wire in one action. These are really nice and useful if you are working under a dash. Manual strippers, which are what most people have in their tool box, cut the insulation only, you have to pull the wire and tool to separate the insulation. Automatic strippers are not very expensive ($20-40) and worth the extra cost if you do much electrical work. Just make sure you use the right size hole for the wire you are working with.
Crimpers– Everything form cheap $3 tools to $200 crimpers are available, but most are in $10-20 range. A good pair of crimpers will last forever and save you many headaches (and blood blisters) along the way. Cheap multi-tool crimpers are junk, stay away from them. You want a tool that can handle at least 3 sizes of crimps- red, blue and yellow insulated terminals. With that, you can accomplish most every job you will face. Specialty crimpers, like the ones required for metri-pack and weather-pack terminals cost a little more and only have the one function.
With these tools in your tool box, there should not be much you can’t handle in a pinch. Don’t forget to keep a roll of 3M Super 33 electrical tape and a service pack of fuses and terminals for those pesky little electrical gremlins that shut you down on the side of the road.