Repair And Fix it

Plug wires arent the most glorious part of any engine, but they are a bit more complicated than most give them credit for being. While wire length may not seem particularly critical, those wires carry an enormous amount of high-voltage power. Pay close attention to your plug wires, or they may end up sending a message that leaves you saying "Can you hear me now?"

Plug Wire Factors

Two things come into play when discussing spark plug wire length: the resistance of the wire in ohms, and the amount of radio frequency interference it produces. The ohm is a measure of a wires efficiency in passing electrical current. Smaller and less-efficient wires rate higher in ohms, meaning that theyll convert more electrical energy into heat in the plug wire instead of passing it to the plug. Resistance in the plug creates a discharge of positive radio waves, which ground out in a cars stereo system and create static through the speakers.

Ohms and Wires

Different grades of wires produce various levels of ohms per foot. An average stock spark plug wire creates about 5,000 ohms of resistance per foot of length; high-performance wires will average between 100 and 400 ohms, and high-grade race wires may go as low as 2 to 10 ohms. If you apply Ohms Law of voltage loss (Voltage Loss = amperes flowing through wire X ohms of resistance) to a typical high-performance ignition system where the coil produces about 20,000 volts and sends about 0.010 amps to the wires, youll find that a stock wire will cause a drop of about 50 volts per foot, a performance wire will drop about 1 to 4 volts per foot and a race wire might drop as little as little as 0.02 volt per foot.

Voltage Output and Plug Length

Since resistance to flow increases by wire length in feet, multiplying the spark plug wires length in feet by its voltage loss per foot will tell you its impact on spark plug power. In the worst-case scenario, assume that a stock 5,000-ohm wire measures a whopping 4 feet long. Thats a 200-volt drop from ignition coil to plug wire -- a seemingly insignificant 1 percent drop. However, that 200-volt energy loss will go into creating heat in the wire, and ohms of resistance go up with heat. The end result is a cascade effect of failure; the current flow and heat gain will eventually reach an equilibrium, but not before producing a noticeable drop in current, damaging the wires conductive core and hindering its RFI-suppressive qualities.

RFI and Solutions

You can get away with using longer plug wires by using a lower-resistance wire, one thats either thicker or higher quality. However, higher current flows also produce more RFI, which means that youll also need to use a high-quality RFI-shielded wire to prevent interference through the radio system. Even if you never listen to anything but MP3s and CDs, remember that RFI interference is an extremely broadband signal. Under certain circumstances, this signal can reach into the frequency ranges commonly used for cell phones and other communications devices, effectively scrambling the signal. So, if your phone seems to constantly drop calls while in the car, you might want to take a look at those old, cheap or mile-long plug wires.

Battery cable corrosion occurs for many reasons, not the least of which is oxidation, a process hard on humans and metal objects. This especially applies to batteries and cables that add corrosive acids and chemicals to the mix. Besides the composition of the battery, another consideration is the battery posts and cables. Mixing dissimilar metals or certain metals together quickly leads to corroded battery cables.

Galvanic Corrosion

A major cause of corroded cables is the mixing of two dissimilar metals when securing the cable to the battery post, which creates a galvanic reaction between the two metals. Three things must be present for this type of reaction: two dissimilar metals with different electrochemical signatures; an electrical path; and a path for metal ions to move from one metal to the cathodic metal. With this two-way path available -- which is how car batteries work when immersed in an electrolytic solution such as sulfuric acid -- a miniature battery develops with current flowing in one direction and the metal ions moving to the stronger metal. This process forms the corrosion seen around the batterys post and cable end.

Battery Fumes

Any kind of venting of battery fumes in or around the battery cables will cause corrosive buildup on the cable ends. This happens when battery cell covers arent secured tightly, or theres a crack in the battery casing, allowing fumes to escape. When corrosion occurs, your battery has to work harder to provide the amperage necessary to start the car. Corrosion that continues to grow can make its way inside the battery and effectively destroy its ability to hold a charge.

Battery Acid

A cars battery contains acid. Besides helping the battery work to store electricity, sulfuric acid acts as a catalyst for corrosion. The acid, when combined with the environment under the hood -- anti-freeze fumes, grease, oil, humidity, dirt and oxygen -- accelerates the corrosion process. Battery cables made from copper are particularly susceptible to corrosion when in contact with sulfuric acid and oxygen.

Prevention

To aid in prevention, ensure cable ends are the same metal as the battery posts. Clean the battery posts with a metal terminal cleaner. For tough cases, use a water-and-baking soda mixture to remove the corrosion, but dont let this concoction enter the battery; this will cause battery failure. Use the brush end of a battery terminal cleaner to hone out the inside of battery cables. After cleaning, apply dielectric grease to the battery posts and cable ends to prevent corrosion buildup. Replace any battery cables that have exposed wires or tears in the sheathing -- these promote corrosion where you cant see it, inside the sheathing itself.

Safety First

When working with a battery, practice safety. Dont smoke around batteries, especially those with the cell covers off; this could lead to explosions. Dont over-tighten battery cable ends -- you could break battery posts. And remove the negative terminal connection before removing the positive to avoid sparks that can ignite fumes.