Electrical And Wiring Guide - Keeping The Magic Smoke Inside
You don’t have to be scared of wiring or electrical work with a little knowledge
From the September, 2011 issue of Modified Mustangs & Fords
By Mark Houlahan
Photography by By The Author
Unlike some repair procedures...
Unlike some repair procedures that require many specialized and/or expensive tools, most electrical repairs or upgrades take very little in the way of specialized equipment. Typically a pair of wire cutter/stripper/crimpers, a 12-volt test light, and a DVOM (digital volt/ohm meter), like these from Snap-on, are at the top of this list.
It's rare to find a car enthusiast who can "do it all." More often than not, when you strike up a conversation with a friend or car owner, you'll find out that he or she lacks the skills to complete certain tasks during the build of their classic ride. A simple question like, "Did you do all of the work yourself?" will usually weed out the weakness of said car owner with an answer similar to, "Well, I did all of the suspension and interior work, but I had my friend build the engine and I sent the body to Acme Painting for all the body and paint work. I just don't know a thing about engines, and paint and body outright frustrates me, so I'm willing to pay someone else to do it." Sound familiar? It does to us, and we hear it constantly when speaking with car owners at events or during a photo shoot.
While we may side with Example A above on the paint and body thing, as it does take some dedicated equipment and room to do it, most any other mechanical upgrade or repair can be tackled with some knowledge, research, and patience. Often you can score some experienced help from a club member or neighbor who will "watch over you" while doing the work. This is how we built one of our first small-block Fords, with a more experienced friend lending a hand and keeping a watchful eye.
Although many classic Ford and Mustang owners are willing to try an intake swap, or recover their own seats, it seems that whenever anything electrical is brought up or considered, said owners turn into rambling zombies about how hard wiring is, and that they don't understand how an electrical circuit works and they might burn their car to the ground. Rubbish, we say! Electrical upgrades or repairs are no different than swapping that intake or recovering those seats; it just takes some knowledge, some common sense, and a few rather inexpensive tools to do the job right and to do it safely.
Whether you're an avid DIY'er, or you're just plain cheap and don't like to pay others for stuff you can do yourself, you owe it to your ride to know the basics of electrical systems and how to repair them or add electrical components. Today's Restomod-type Mustangs can feature everything from completely upgraded whole-car wiring harnesses to power windows and locks, electronic ignition upgrades, and even fuel injection.
A simple electrical connection made incorrectly or a small wiring issue, such as a left rear turn signal that doesn't blink, can wreak havoc on your time and patience, so we've put together some basic electrical help in this story. We'll show you the tools you'll need, and what to look for in an electrical failure, such as a wiring short or an open circuit. We'll discuss basic electrical upgrades, circuit protection, wire sizing, and more. We simply don't have the room to cover every wiring scenario or upgrade, nor the space to delve into electrical theory, but we hope to give you the confidence to head to the garage and tackle that wiring issue you've been avoiding. So take a deep breath and read on.
Book 'em Dano!
Automotive Wiring and Electrical Systems
No matter how much automotive education one might possess, we all have our weaknesses. The one area that we see the majority of people struggle with is automotive electrical systems. From simple things like wiring a relay into a fan circuit to adding aftermarket car audio and gauges, many of us work with electrical systems on our projects with trepidation. With Automotive Wiring and Electrical Systems by Tony Candela, you can now upgrade or repair your vehicle's electrical system like a pro.
Tony takes you by the hand right from Chapter 1, and introduces you to the proper tools for automotive electrical repairs and upgrades, how to test circuits, build wiring harnesses, and more. There are even pre-designed wiring diagrams for popular upgrades like adding power door locks and much more. You’ll find this book at booksellers nationwide or you can order online at www.cartechbooks.com or phone order at (800) 551-4754.
1 For tight working locations,...
1 For tight working locations, especially under the dash, an automatic wire stripper, like the one shown here, allows for easy one handed operation without requiring the typical two-handed stripper/crimper that can get in the way.
2 Another great solution...
2 Another great solution for tight quarters are these mini tools from Sears Craftsman. They work great for cutting, stripping, and crimping operations where space is at a premium.
3 Yet another crimping solution...
3 Yet another crimping solution is a set of ratcheting crimpers. If you have a habit of over-crimping a wiring connection, a set of ratcheting crimpers will do the job properly every time without over-crimping.
If you’re going to walk the walk you need to be able to talk the talk, and that means knowing the difference between a diode and a resistor, and where and when you need to use them. So bone up on these electrical terms and be ready for that pop quiz!
AWG (American Wire Gauge): An industry standard specification for wire size, the larger the number the smaller the diameter of the wire.
Battery: A multi-cell electrical storage device used as a source of power.
Circuit Breaker: A resettable switch that disengages in the event of excessive electrical amperage (they can be manually or automatically reset).
Current: The flow of electricity through a conductor (circuit, wire, and so on).
Diode: A semiconductor that allows current flow only in one direction.
DMM/DVOM (Digital Multimeter/Digital Volt/Ohm Meter): An electronic tool that measures several electrical ranges in one tool, including AC and DC voltage, current, and resistance.
Fuse: A device that interrupts the flow of current through a circuit if the amperage exceeds the rating of the fuse.
Fusible Link: Similar to a fuse, the fusible link is a section of wire four AWG sizes smaller than the wire circuit it protects, melting “open” in the case of excessive current.
Open Circuit: A wiring circuit that is incomplete, usually a broken or disconnected wire.
Parallel Circuit: A circuit where all connections are parallel to each other. Dash illumination is an example of a parallel circuit.
Relay: A device that uses one circuit to turn off or on another circuit, usually of a higher amperage.
Resistance: The opposition of electrical current flow through a circuit or wire, measured in ohms.
Resistor: An electrical component that limits/regulates the current flow through a circuit.
Series Circuit: A circuit where the electrical connections are wired end-to-end. Early Christmas tree lights are an example of series wiring.
Short Circuit: A condition where a wiring circuit has no resistance, typically a short is a wire carrying voltage touching ground, causing an alternative voltage path.
SPDT (Single Pole/Double Throw): A type of switch that connects a common pole to either of two contacts.
SPST (Single Pole/Single Throw): A type of switch that connects a common pole to one contact that can be turned off or on.
Voltage: The measurement of potential electrical energy to move electrons from one point to another.
4 Using a test light is a...
4 Using a test light is a simple way to verify if a circuit has power or ground, simply by connecting the alligator clamp end of the lead to a known power or ground source (usually the battery), and probing the circuit with the end of the test light. If the test light illuminates, you have power or ground (depending upon which terminal the lead is clamped to). For more sensitive circuits, such as EFI computers, it’s better to use the aforementioned DVOM to check for voltage or ground signals.
5 Circuit protection comes...
5 Circuit protection comes in many flavors. From the old-school glass fuses to modern ATO blade fuses, fusible links, and more. It’s imperative that for any add-on circuits you plan that they be protected. Usually the installation instructions will tell you what the fuse size needs to be, but if it isn’t stated, you can usually determine what is needed with a little basic math. See our sidebar on Tony Candela’s book where you can learn all about Ohm’s Law and more to determine proper fuse protection.
6 Probably the number one...
6 Probably the number one issue we’ve seen with electrical systems is a ground problem. Oftentimes a ground will come loose, become degraded by corrosion, or simply be missing. Always take a second to gather your diagnostic thoughts and check your grounds. A solid engine-to-frame ground, like the one shown here, solves a lot of problems under the hood with gauges, ignition systems, and more.
7 Most of our readers are...
7 Most of our readers are probably familiar with the solderless terminals shown here. These insulated connectors come in handy when repairing a circuit or adding an electrical item to your car. They allow the joining, connecting, or termination of a wire to a device or another wire. As noted earlier, they can be over-crimped. If you haven’t used these before, it’s best to practice with some scrap wire and extra terminals. They come in many types, including seamed, seamless, with or without shrink wrap coating, and more. Know your connector and how they should be crimped.
8 While the solderless terminals...
8 While the solderless terminals in the previous photo caption get the job done, we prefer to use the non-insulated terminals like the ones shown here. The terminals are essentially the same; you just have to insulate them yourself with shrink wrap. These terminals have a smaller footprint, so they hide easier inside a wiring harness and look more professional when connected to a visible device like a starter solenoid or an ignition coil. Never use a non-insulated terminal without covering it with tape or shrink wrap.
9 One thing you should never...
9 One thing you should never consider for any sort of permanent repair, modification, or upgrade are so called “tap” connectors. Every time we’ve seen these things in a wiring harness there’s some sort of issue that can be traced back to them. We only consider using them for an emergency repair or temporary use. You’ve been warned.
10 Something new on the market...
10 Something new on the market in the way of tap connectors are these special threaded taps called Posi-Taps from Posi-Lock. They are easy to use and can be used in a permanent installation situation. The complete Posi-Lock line can replace typical crimp connectors and make for great tool-free emergency repairs. Check out www.posi-lock.com for more info.
11 As we mentioned in caption...
11 As we mentioned in caption 10, the non-insulated terminals with a small section of black shrink wrap over the crimp section looks more professional than seeing a bunch of blue, red, and yellow terminals all over your engine bay.
12 Adding a wiring circuit...
12 Adding a wiring circuit to your classic Ford is a common occurrence, but what happens when it’s a year or two down the road and you’re under your dash staring at a wire and wondering what it goes to? The easy answer is to add a tape flag to the end of the circuit. We like to use the thermal label printers you can find at the big box stores. You can also label relays to remember what they are for with labels that say “Fan,” “Fuel Pump,” and so on.
13 When installing a whole-car...
13 When installing a whole-car wiring solution, you’ll often find extra circuits in the harness you won’t be using. It’s tempting to cut the wiring off at the fuse box or connector, but do yourself a favor and leave the wiring in place for future upgrades. Use a short section of shrink wrap on the cut wire end and then squeeze it shut with pliers. This will ensure the wires won’t short to anything and can easily be used in the future.
14 Whenever you have wiring...
14 Whenever you have wiring passing through a firewall, bulkhead, or other steel panel, you have to protect the wiring from shorting to the panel by using a grommet or bushing. A rubber grommet or plastic bushing is easily popped into a drilled hole, allowing the wiring to pass through safely. Don’t rely on the wiring casing or some electrical tape to protect the wiring alone.
15 A crispy mess like this...
15 A crispy mess like this can only be repaired properly with the right wiring diagrams. Today, classic Mustang diagrams have been reproduced in full color and are available from many parts vendors. Don’t go it alone; get the diagrams and save yourself much time, aggravation, and headache so you can make a proper repair. The issue here was caused by a shorted power wire that caused excessive heat, melting the surrounding wire’s insulation together.
16 The basic test light can...
16 The basic test light can also detect current flow besides the aforementioned voltage and ground testing. Simply connect the test light between the battery terminal and cable clamp as shown to detect any current flow that could be causing a battery drain. Ensure the key is off and doors are closed. If you have a measurable drain, look for sticking console or glove box lights, or bad electronic hardware. Pull your fuses one at a time until the light goes out and you’ve found your circuit causing you problems.
17 The digital volt/ohm meter...
17 The digital volt/ohm meter (DVOM) is a more accurate way to measure current, resistance, or voltage. The typical DVOM has a dial to choose the proper scale for measuring each, along with a selection of test lead ports to connect the leads to. To check for voltage, use the VDC scale, while resistance is measured on the ohm scale (Ω). You use a different lead port and scale (mA or A) for checking current draw. You also want to make sure there’s no voltage present in the circuit when checking resistance. Sure, the test light is lit in the previous caption, but what’s the amount of current passing through it? The current flow could be normal, like a memory circuit, or it could be an actual problem. Connect the DVOM in the same manner as the test light (ensure you have the test leads plugged into the proper ports on the meter!) and then read the actual amperage of the current flow, which is 3.308 amps in this case because we have the parking lights turned on.
18 Building a custom wiring...
18 Building a custom wiring harness for your aftermarket gauges or perhaps for those power window switches you’re adding to your console? Take the time to draw up a diagram of the circuit, including the connector pin outs with wire colors. Put the diagram in your project car binder and you’ll always have an easy way in the future to refer back to what wire does what and where it goes.
19 Far too often we find...
19 Far too often we find wiring issues caused by the wrong connector or terminal being used in an open environment. Today’s cars use weather-tight connections anywhere outside of the passenger compartment. If you’re rewiring your classic Ford, or adding any exterior circuits (driving lights, electric fans, and so on), make the effort to use a weather-tight connection. You can purchase a kit with multiple connectors, weather seals, terminals, and even the crimping tool from DIYAutotune (www.diy autotune.com).
20 Protection of any add-on...
20 Protection of any add-on wiring is just as important as the connection of the wiring. Having individual wires routed everywhere and secured with a tie wrap or two doesn’t cut it. All accessory wiring should be inserted into some sort of protective cover, like the common split-loom. Furthermore, wrapping the split loom with harness tape (not electrical tape) is even better, as it makes the harness water tight and OE in appearance. The retaining clamp shown is from Mr. Gasket and they work great for retaining wiring via screws or rivets.
21 If a repair is going to...
21 If a repair is going to take more than one wire run, do yourself a favor and use different color wiring. You can purchase wiring in spools and you should have at least four colors on hand in the popular AWG sizes (red, black, and two other colors). You can often find a wiring spool center or rack with sample wiring lengths, or you can buy your own spools and make your own rack.
22 There’s an old wife’s...
22 There’s an old wife’s tale that soldering wires is a big no-no in automotive wiring. There’s nothing wrong with soldering for automotive use, provided you know how to solder. Explaining a proper solder connection is an article unto itself, but if you know how to solder, by all means feel free, but if not, stay with a quality crimp connection for your repairs (or learn to solder!).
23 You might find yourself...
23 You might find yourself needing to install a switch to control a circuit in your car. There are several types of switches, and we’re not referring to color or size here. No, we’re referring to the number of poles and how many poles are connected at one time. SPST, SPDT, DPDT, latching, momentary, and so forth. Your best bet is knowing what switch to use in the first place. Once you know what these switches/toggles are and how they work, you’ll know exactly what you’ll need.
24 While we’re limited in...
24 While we’re limited in room for this article we’d be remiss if we didn’t at least briefly mention wire sizing, as that is one of the top reasons for circuit failure. We see way too many cars with improperly sized wiring. It’s confusing, like gear ratios, that the larger the number, the smaller the wire. You can easily find wiring charts online and in books that explain the proper gauge for typical connections so you won’t be wiring up that electric fan with 18-gauge wiring.