7 Common Electrical Problems in Heavy-Duty Trucks—and How to Fix Them in Casper, WY

7 Common Electrical Problems in Heavy-Duty Trucks—and How to Fix Them in Casper, WY

When it comes to keeping heavy-duty trucks rolling through tough terrain and unpredictable weather, like we get in Casper, WY, electrical reliability is non-negotiable. A failed starter, shorted headlight, or mysterious dashboard warning can sideline even the most well-maintained rig. 

Unfortunately, electrical problems don’t always come with warning lights or easy fixes. Here are seven of the most common issues in modern trucks, along with practical tips to fix them before they turn into downtime disasters.

1. Dead Batteries and Charging Issues

Let’s start with the obvious: a broken battery. Battery failure is one of the leading causes of no-start conditions. Combine long idle times, harsh Wyoming winters, and parasitic draw from onboard electronics, and it’s no wonder batteries suffer.

Common causes:

• Alternator failure
• Loose or corroded terminals
• Parasitic draws from accessories
• Worn-out or mismatched batteries

Perform voltage drop tests on cables. Check alternator output (should be 13.5–14.8 volts under load). Replace both batteries together if one fails; mixing old and new batteries shortens lifespan.

2. Faulty Ground Connections

If your truck’s electrical system seems to be possessed, flickering lights, random warning chimes, erratic gauges—it might not be a component issue at all. It could be a bad ground.

Ground faults cause:

• Inconsistent electrical signals
• ECM communication issues
• Voltage drops across circuits
• Complete module shutdown

Check and clean ground straps. Use a multimeter to confirm continuity between the chassis and the battery negative. Re-torque ground connections, especially after chassis repairs or framework.

3. Lighting System Failures

In rural Wyoming or nighttime hauls, reliable truck lighting is a must. Whether it’s marker lights, headlights, or trailer tail lamps, wiring and connection issues are common and DOT violations waiting to happen.

Frequent causes:

• Corroded connectors from road salt
• Broken or pinched trailer harnesses
• Faulty bulbs or LED driver failures
• Improperly installed aftermarket lighting

Inspect lights during every pre-trip. Use dielectric grease on connectors. Upgrade to sealed harnesses if operating in wet or icy environments.

4. CAN Bus Communication Errors

Today’s trucks aren’t just mechanical—they’re rolling computer networks. The Controller Area Network (CAN Bus) connects everything from ABS to HVAC. A failure in communication can disable entire subsystems.

What to look for:

• Multiple warning lights triggered at once
• Loss of dash communication or gauges
• Codes from multiple modules with no clear root cause

Start with the basics: battery voltage and clean power. Then check for proper termination resistance on the CAN line (typically 60 ohms). Inspect for chafed wiring and water intrusion at module connectors.

5. Starter Motor or Solenoid Failure

A truck that won’t crank, but has power, is likely dealing with starter issues. In high-mileage rigs, worn solenoids and tired starter motors are common, especially in cold climates.

Symptoms include:

• Clicking but no crank
• No sound at all on the key turn
• Intermittent cranking

Test starter draw with an amp clamp. Inspect relay and solenoid wiring for corrosion. If the starter is original and high-mileage, replacement is often more reliable than rebuild.

6. Faulty Sensors and Intermittent Codes

Modern emissions and drivetrain systems depend on sensor accuracy. When a sensor fails—or provides inaccurate readings—it can cause derates, regen issues, or limp mode conditions.

Common sensor failures:

• MAF (Mass Air Flow) or MAP (Manifold Pressure) sensors
• Exhaust Gas Temperature (EGT) sensors
• DPF differential pressure sensors
• Crankshaft or camshaft position sensors

Use scan tools to monitor sensor data in real-time. If readings are erratic or out of range, replace with OEM-quality parts. Always inspect connectors and pigtails for signs of moisture intrusion or damage.

7. Wiring Harness Damage

One of the most frustrating, and common, electrical problems is damaged or chafed wiring harnesses. Between road vibration, tight engine compartments, and heat exposure, it’s not a matter of if.

What you’ll see:

• Short circuits
• Blown fuses
• Intermittent electrical faults
• Random code clusters

Trace harness routes during inspections. Use protective loom and secure mounting clips to avoid rubbing. In colder climates like Casper, look out for rodent damage—especially in trucks stored outdoors.

Electrical Know-How Saves Downtime

Today’s heavy-duty trucks are more electrified than ever. From DEF dosing systems to fully electronic HVAC controls, a simple wiring issue can cripple your rig. But with consistent inspections, proper testing tools, and a trained eye for weak spots, you can stop electrical issues before they cost you contracts, drivers, or DOT compliance. 

At Central Truck & Diesel Inc in Casper, WY, we specialize in full-system electrical diagnostics and repair for commercial trucks—keeping you powered, productive, and always road-ready. To learn more, read our article to see if your truck’s electrical system is draining your battery.