5 Signs Your Liftgate Wiring Harness Needs Immediate Repair

Your Liftgate Is Only as Reliable as Its Wiring

In the fast-paced world of commercial trucking and delivery logistics, liftgates are a vital tool. They ensure cargo is safely loaded and unloaded—especially where loading docks aren’t available. But if the wiring harness that powers your liftgate is compromised, the entire system becomes unreliable, dangerous, or downright unusable.

At Dog House Trailer Repair, we regularly troubleshoot liftgate failures—and nine times out of ten, the culprit is a worn, damaged, or neglected wiring harness. The good news? These problems show clear warning signs if you know what to look for.

Here are five unmistakable symptoms that your liftgate wiring harness needs immediate repair—and what to do before it fails in the middle of a delivery.

1. Intermittent Power or Operation

The Sign

You press the liftgate switch and—nothing. Or maybe it works one minute, then goes dead the next. The gate might start to lift, only to freeze mid-cycle. These unpredictable failures are often mistaken for a bad switch, but they’re usually caused by internal wiring issues.

What’s Happening

Over time, the wiring harness can experience:

• Broken wires from repeated flexing
  
  
• Loose terminals or connectors
  
  
• Moisture ingress causing intermittent shorts
  
  
• Corrosion at plug connections
  
  

A damaged harness loses continuity, meaning the electrical signal doesn’t consistently reach the hydraulic pump or solenoids.

What to Do

Inspect the full length of the harness—especially at pivot points and near the trailer frame. Look for exposed copper, frayed insulation, or pinched sections. Test continuity with a multimeter and check voltage under load. If the harness fails any of these tests, replacement is recommended.

2. Blown Fuses or Tripped Breakers

The Sign

Your liftgate circuit keeps blowing fuses or tripping the truck’s breaker. You may find yourself constantly replacing fuses just to keep working.

What’s Happening

This is a strong indicator of a short circuit somewhere in the liftgate wiring. It could be due to:

• Cracked insulation allowing wires to ground out on the frame
  
  
• Water intrusion into connectors
  
  
• Corrosion causing excessive resistance
  
  
• Internal abrasion of wires inside the harness jacket
  
  

Blown fuses protect your system—but frequent fuse failure is your system crying for help.

What to Do

Don’t just replace the fuse and hope it holds. Visually inspect the harness, especially at bends, tie-down points, and where the harness enters junction boxes. Check for signs of arcing or melted insulation. Repair or replace the damaged section immediately before it causes more serious electrical damage.

3. Slow or Weak Liftgate Function

The Sign

Your liftgate still moves, but it’s sluggish. It lifts slowly, struggles under load, or sounds like the motor is working harder than it should. This is often blamed on the hydraulic system—but the wiring harness may be to blame.

What’s Happening

Electrical resistance within a corroded or damaged harness reduces voltage to the liftgate motor. That means less power, slower pump operation, and overheating under strain. Even a 10% voltage drop can result in noticeable performance loss.

What to Do

Use a voltmeter to measure voltage at the motor terminals during operation. If it reads significantly lower than battery voltage, the harness may be causing a voltage drop. Trace the wiring and clean or replace any corroded terminals, crimped wires, or overloaded relays.

4. Exposed or Damaged Wire Insulation

The Sign

You see exposed copper strands, cracked insulation, or missing loom along the liftgate harness. Even if the liftgate still works, you’re operating on borrowed time.

What’s Happening

Liftgate harnesses are exposed to road debris, UV radiation, ice, salt spray, and constant movement. Over time, the protective insulation wears away, leaving conductors vulnerable to shorting, moisture intrusion, and physical damage.

What to Do

Don’t patch it with tape and move on. Exposed wiring should be repaired with heat-shrink connectors, sealed junctions, and proper protective loom. If more than 30% of the harness is compromised, a full harness replacement is the safest long-term solution.

5. Liftgate Doesn’t Work in Wet Conditions

The Sign

Everything functions fine—until it rains. After a downpour or during winter road slush, your liftgate refuses to operate or trips the breaker. Then it starts working again once everything dries out.

What’s Happening

This is a classic sign of moisture intrusion in the wiring harness or connectors. Water enters damaged plugs, cracked insulation, or poorly sealed junction boxes. Moisture bridges connections, causes arcing, and shorts out the system.

What to Do

Inspect all connectors and plugs for signs of water. Open any sealed junction boxes and look for corrosion or water pooling. Use dielectric grease on all electrical connections and replace any connector that shows green corrosion or loose fitment. A waterlogged harness should be replaced as soon as possible to avoid further electrical failure.

Why Liftgate Harness Issues Can’t Wait

A failing wiring harness isn’t just an inconvenience—it’s a safety risk. If a liftgate fails under load, cargo can be damaged, drivers can be injured, and delivery schedules thrown into chaos. Worse yet, repeated short circuits can damage expensive components like solenoids, motors, or even the truck’s main fuse panel.

At Dog House Trailer Repair, we don’t patch bad harnesses—we fix the root cause. We offer:

• Full wiring harness replacements
  
  
• Diagnostic voltage and load testing
  
  
• Waterproof connector upgrades
  
  
• Harness routing and retention to prevent repeat wear
  
  
• In-shop or mobile liftgate diagnostics for fleets
  
  

How to Prevent Liftgate Wiring Issues in the Future

Use Quality Connectors and Loom

Cheap connectors are the first to corrode. Always use weather-sealed, marine-grade terminals, and protect wiring with UV-resistant conduit.

Secure Harness Routing

Harnesses that rub against sharp edges or suspension components wear out fast. Secure with grommets and tie-downs to prevent unnecessary movement.

Add Moisture Protection

Apply dielectric grease to every connector. Install drain holes in junction boxes and avoid low spots where water can collect.

Perform Periodic Voltage Testing

Even when everything seems fine, check voltage at the motor and solenoid during PMs. Drops in voltage reveal problems before failure occurs.

Schedule Regular Inspections

Add liftgate harness checks to your regular preventive maintenance checklist. This should include visual inspections, continuity testing, and a function check during wet conditions.

Final Thoughts

Your liftgate wiring harness works hard, out of sight and under pressure. But when it fails, it takes your productivity down with it. Don’t wait for total failure before acting.

If you’ve noticed any of the signs above—or just want peace of mind before your next route—schedule a diagnostic with Dog House Trailer Repair. Our techs specialize in liftgate systems and will keep your trailer powered, compliant, and delivery-ready.