Automotive wiring has a tough job to do. It must operate in adverse conditions such as extreme heat 
and cold, vibration, moisture, and chemicals. Chemical corrosion has increased over the years due to the use of magnesium chloride and calcium chloride as anti-icing agents instead of salt. Taken together, all these factors can cause connectors to corrode and wires to pull out, resulting in equipment downtime and repair costs.
Here are few tips to extend the life of your automotive wires and connections and keep them functioning in top form.
1. Sealed Connectors and Heat Shrink
Consider using heat shrink terminals and connectors in place of non-insulated, vinyl or nylon-insulated options. A high-quality sealed connector protects against moisture and contaminants that cause corrosion. 
Heat shrink connectors are constructed with adhesive-lined polyolefin heat shrink tubing to seal out moisture. Their initial cost is a little higher than non-insulated, nylon, or vinyl electrical connectors, but they offer substantial environmental protection, easy installation, and durability, making them well worth the investment.
Shown at right: Example of a heat shrink butt connector from Molex.
Heat shrink tubing is another option to provide an added measure of protection. It can be used for a variety of applications including wire insulation, cable bundling, and strain relief. For a quick overview, see our article Heat Shrink 101.
Heat shrink tubing, as the name implies, shrinks when heat is applied, providing a tight seal.
2. Battery Terminal Covers
Battery terminal covers (also called battery boots) are an inexpensive and simple way to keep your battery cables and battery connections clean and corrosion free.
Typically made of vinyl or rubber material, battery terminal covers are flexible and easy to install over copper eyelets and battery lugs of any size ranging from 18 gauge to 4/0 gauge.
Right: Battery terminal covers or “boots” are usually sold in black or red for color coding and easy identification of cables
3. Strain Relief
Shown here: A right-angle heat shrinkable cable entry seal from TE-Raychem.
4. Thermal Protection
Heat is another stressor on automotive wire. Internal combustion engines are essentially powered by explosions. As fuel burns, heat builds and can wear out wiring connections and melt insulation, creating not only an electrical problem but also a fire risk. In addition, the natural resistance of the wire means it will also heat up when current runs through it. Wire sleeving made of aluminum or fiberglass can help protect your wires against heat and prevent broader safety problems in your vehicle.
Right: Protective wire sleeving wrapped with reflective aluminum foil, by Delfingen
5. Compartment Sealing
Work vehicles are at risk of intrusion by water, salt, chemicals, and even small animals that might damage your wiring. There's only so much abuse a wire or connection can take before problems arise. Sealing your compartments with liquid-tight hole plugs, locking hole plugs, and electrical tape can help keep them free of intrusion.
Right: A Liquid-Tight Hole Plug from Heyco.
6. Circuit Protection
One of the biggest threats to automotive wire is electricity itself. There are many reasons that wiring might suddenly carry a heavier electrical load than intended, but the result can wreck your wiring and potentially make it dangerous to turn the ignition key.
Your electrical system should be properly protected against shorts, surges, and other problems. A fuse or circuit breaker in the right place can make the difference between a functioning vehicle and a stalled one waiting to be towed. For more information see Fuses 101 and A Basic Guide to Circuit Breaker Types.
7. Dielectric Grease 
Make periodic use of dielectric grease, especially before winter and in cold climates. Applying dielectric grease to electrical connections such as spark plug boots, battery terminals, and headlamp connectors helps ensure the longevity of your connection points. It creates extra insulation for electrical connectors, helps ensure a proper seal, and prevents arcing (i.e., current jumping from its intended path). Dielectric grease is ideal for electrical connections with rubber gaskets.
Shown at right: Dielectric Grease from Dynatex
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If electricity and fuel are the lifeblood of your vehicle, automotive wire is the brain and nervous system that keeps it all working smoothly. Protecting your electrical system with the simple techniques outlined above will help keep your vehicle in good shape and prevent unneeded headaches down the road.
