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Avoid the Top 10 Electrical Snafus

How Not to Look Like an Electrical Moron by Avoiding the Top 10 Classic Electrical Snafus

Photography by , Mark Hamilton, Terry McGean


It's standard: You overkill the positive side of the 12-volt circuit andignore the ground circuit. Basic electrical circuit design requires acomplete path back to the battery through the ground circuit, and if ithas high resistance, then the electrical device will operate poorly.

Bad grounds happen everywhere, but the worst case is when guys relocatethe battery to the trunk, run a nice, thick multi-strand cable from thebattery to the starter solenoid, then merely bolt the ground cable tothe trunk floor or other easily accessible spot and leave it at that. Avoltage-drop test (see page 58) on that ground circuit will probablyreveal an inexcusable 1.5- or even 2-volt drop across the ground side ofthe circuit. The starter may crank when it's cold, but not onceeverything warms up (remember, resistance increases with temperature).The fix is to either run a large ground cable all the way up to theengine, or a large ground from the battery to the frame and another fromthe frame to the engine.

Another common grounding failure is an electric fuel pump pulling 4 to 5amps. We often see pumps wired with a small, 14-gauge positive cable andfurther crippled with a corroded piece of piano wire for a ground.Improve the ground circuit with a larger 12-gauge wire and ensure thatthe ground circuit offers no more than 0.1-volt drop and the fuel pumpwill run much more efficiently.

The most dangerous bad ground comes from weak or small-wire groundsbetween the engine and the chassis and between the chassis and the body.These create resistance that can quickly overheat and in extreme casesbegin to melt and catch fire. It sounds implausible, but keep in mindthat the ground circuit must complete the current flow, so the groundside must always be as bulletproof as the positive side of the circuit.


Every auto parts store in the country offers those cheesy crimpconnectors with the little plastic sleeves that are supposed to providea great connection. The problem is that these temporary fixes soonbecome permanent. Certainly one of the least effective electricalconnectors has to be that one that pinches two parallel wires, hoping tomake a connection. If you find one of these connectors in your car, cutit out immediately. And when you get them in the box with a newelectrical goodie--especially a nitrous system--chuck them as far as youcan.

There is some controversy over the proper way to make an electricalconnection. Fans of solder will tell you that it prevents corrosion, butits detractors say it's too brittle and will eventually fail immediatelyadjacent to the connection. The problem with crimp connections--evenwhen protected with shrink wrap--is that they are sources for corrosion.Either way, the following steps outline the right way to perform anelectrical connection.


Often the alternator is blamed for poor charging when the problem isactually bad wiring or connections. So try this quickie test. With theengine running, check the voltage at the output terminal of thealternator; on Terry McGean's Camaro, we found a high 15.7 volts. Next,measure voltage at the battery; McGean's was barely 13.5 volts, a lossof 2.2 volts in a circuit that should lose no more than 0.4 to 0.5. TheCamaro suffered from multiple broken strands in the charging wire andseveral corroded connections. We added a large-diameter charging wirefrom a Painless Wiring high-amp alternator kit and improved theconnection between the battery and the junction block using a MADterminal block. Voltage drop across the circuit improved to 0.5 volt.Furthermore, by reducing resistance in the charging circuit, thealternator output voltage dropped back to a more reasonable 14.7 voltswhile voltage at the battery measured 14.2 volts.


Let's hope the positive battery post on your musclecar doesn't look likea bowl of spaghetti. Combine that with a typical unsealed battery andthe connections quickly become corroded and nasty. The solution is tomove all those wires off the positive battery post and onto a separateterminal block. MAD offers an inexpensive one (PN CN-1) that canaccommodate several 8-gauge wires to power multiple accessories. This isalso a great idea for an underhood power source for cars with thebattery in the trunk. This block can be used to power up an MSD,electric fans, an A/C, and solenoids for nitrous along with at least adozen other ideas. Hide this under the fenderwell and carefully routeyour wires and you'll be amazed how clean your engine compartment willbecome.


Many slow cranking problems can be traced to high-resistance cables.Using high-quality MAD or Painless battery cables is the obvioussolution. The MAD cable is impressive 1/0 gauge multi-strand copperconductor that is also double insulated. If the starter just grindsslowly, this is a voltage-drop problem. But if you've got the typical GMproblem of the starter not engaging properly in a hot-soak condition,the cause is a major voltage drop across the solenoid-engagementcircuit. The fix is as simple as using a Ford-style external solenoid ina kit from either MAD or Painless. The idea is simple: Mount thesolenoid away from exhaust heat, which radically reduces the voltagedrop across the solenoid circuit. Both kits also supply a shunt thatconnects the solenoid battery cable terminal to the small trigger post.Another advantage is that if you use one of these kits with atrunk-mounted battery, the only time the battery cable downstream fromthe solenoid is "live" is when the starter is engaged. This is a smallpoint, but worthy of consideration from a safety standpoint.

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