Issue link: https://read.dmtmag.com/i/26876
BIG RIG BASICS JOHN BAXTER Main Overload! hen something goes wrong in wiring or an acces- sory, the flow of electrical current can create heat that damages wiring and accessories or even starts a fire. Fuses contain a soft conductor that melts easily. When a short circuit or overload happens, the fuse will quickly melt and break the circuit, killing power to it before there is too much heat. Self-resetting circuit breakers are often substituted for fuses. They work like a thermostat, reacting to the heat created when current flows through them. Since wiring can handle an intermittent over- load without overheating, these devices “reset” themselves after a short cooling off period, switching back on. W A Proper fuse maintenance will help you contain the high costs incurred by electrical damage. Here’s how to replace them and ensure continued reliability CHANGING FUSES B Level of difficulty (scale 1-5 with 5 being the hardest job): 2 Tools required: Narrow-jawed or needle-nose pliers (DSCN0790), rags for drying fuse box covers when under the hood Time: Less than 15 minutes The latest vehicles may have small fuse boxes distrib- uted around the vehicle, often incorporating electronic monitoring and control of circuits for pro- tection, with fuses as backup. When a cir- cuit fed by one of these starts to shut off intermittently, the problem is in the wir- ing, not a blown fuse. A You can tell a fuse is blown by look- ing through the clear plastic B. You’ll see solid, bright metal when it’s OK and a separation in the metal when it’s blown. When a fuse blows, Freightliner of Phila- delphia Service Manager George Bollinger says to suspect electrical trouble. But since fuses are softer than wiring and can fail, and they’re inexpensive, it’s worthwhile to try one replacement to BIG RIG BASICS TIP SEAN GLEN HAS A 2003 KENWORTH W900 WITH A CATERPILLAR C16 ENGINE. The truck has only self-resetting circuit breakers. “When a fuse blows, you can see it,” he says. “But there is no way to test a circuit breaker or know it’s bad.” He suggests carrying a duplicate set — one breaker of each amperage rating — in your fuse box. When a breaker starts to constantly reset or seems to have blown out, replace it. If the new breaker does the same thing, you will need to get the wiring problem diagnosed and repaired. 26 TRUCKERS NEWS APRIL 2011 Sean Glen