Common failure points in EV trucks and how to choose replacement parts

EV trucks are increasingly becoming part of the mainstream fleet in the U.S. As their numbers grow, so does the need to understand their maintenance challenges. While electric trucks tend to have fewer moving parts than internal combustion (ICE) trucks, they are not immune to failures. In fact, some components unique to EV trucks become critical points of failure, and choosing the right replacement parts is essential to reliability, safety, and cost control.

In this article, we’ll explore the most common failure points in EV trucks, why they occur, how to spot early signs, and detailed guidance on how to choose quality replacement parts. We’ll also include a robust FAQ section addressing what people commonly ask. The goal is to equip buyers, repair shops, fleet managers, and DIYers with clear insight into EV truck part sourcing and selection.

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Common Failure Points in EV Trucks

Here are the major subsystems or components in EV trucks that tend to fail or degrade over time (or be subject to damage). For each, I’ll explain the failure modes and contributing factors.

1. Battery Pack and Battery Management System (BMS)

2. Traction Inverter / Power Electronics / Converter Modules

3. Electric Motor / Drive Units

4. High-Voltage Wiring, Connectors, and Cabling

5. Charging System Components (Onboard Charger, Port, Cables)

6. Thermal Management and Cooling Systems

7. Low-Voltage / Auxiliary Electrical System

8. Suspension, Chassis, and Wear Items (Brakes, Bearings, Bushings)

9. Sensors, Control Modules, and Software (ECUs, CAN network)

10. Safety Systems (Fuses, Disconnects, Contactors, Relays)

Let’s unpack these in turn.

1. Battery Pack & Battery Management System (BMS)

Why it fails / degrades:

• Battery cells naturally degrade over time, reducing capacity and range.

• Fast charging, deep discharge cycles, heat stress, and improper charging habits accelerate degradation.

• Cell imbalances can occur, where some cells age faster than others, leading to weaker modules dragging performance.

• The BMS (Battery Management System) monitors and balances cells; if it malfunctions, it may mis-report state of charge, misbalance cells, or even shut down parts of the battery.

• Thermal runaway or internal shorts (rare) can lead to catastrophic failure.

• Physical damage (collision, puncture) can damage battery modules or wiring.

Signs / early symptoms:

• Rapid drop in driving range (worse than expected).

• One or more battery modules are flagged or disabled by the system.

• Inconsistent charging behavior or inability to fully charge.

• Warning lights or fault codes related to battery or BMS.

• Heating issues or unusual temperature unbalance in modules.

Replacement / repair considerations:

• Batteries are expensive; repairing or reconditioning modules (if possible) is often preferred over full replacement.

• Ensure any replacement or refurbished module is compatible (same chemistry, voltage, module design).

• The BMS must match the battery architecture (number of cells, communication protocol).

• Prefer OEM or high-quality aftermarket modules with good warranty and proven history.

• Check for safety certifications, thermal protections, and overcurrent protections.

• For modular battery packs, replacing only the damaged module is more cost-effective; but some designs are not modular.

• Ensure proper cooling integration and sensors are present in the replacement.

• Document and calibrate cell balancing after replacement.

2. Traction Inverter / Power Electronics / Converter Modules

Why it fails:

• The inverter and associated power electronics (DC-to-AC inverter, DC-DC converters) experience high electrical loads, switching stress, heat, and voltage transients.

• Use of wide-bandgap semiconductors (SiC, GaN) helps but introduces sensitivity to temperature and switching stress.

• Overheating, voltage spikes (due to load or load rejection), component aging, or manufacturing defects can degrade MOSFETs, IGBTs, capacitors, and gate drivers.

• Poor cooling or thermal cycling can stress solder joints and degrade internal paths.

• Electrical overstress (EOS) or voltage surges may cause catastrophic failure.

Signs / early symptoms:

• Loss of traction, inability to drive, or limp mode.

• Sudden power drop or motor derating.

• Persistent fault codes for inverter or powertrain.

• Unusual noises, smells, or overheating around the electronics housing.

• Inconsistent motor response or electrical instability.

Replacement / repair considerations:

• Replacement units must match voltage, current rating, cooling interface, and control interface.

• OEM or high-reliability aftermarket parts are preferred — avoid cheap imitation units.

• Ensure proper thermal management (heatsinks, coolant, sensors) is reinstalled or upgraded.

• Module-level repair is possible (replacing MOSFETs, driver boards), but demands advanced test equipment and matching.

• Compatibility with vehicle’s control software and firmware is essential.

• Consider components with protective features (overvoltage, overtemperature, desaturation detection) built-in.

• Document input and output connectors, pinouts, and cooling connections meticulously.

3. Electric Motor / Drive Units

Why it fails / degrades:

• Electric motors are relatively robust but are not immune to defects: bearing wear, insulation breakdown, rotor faults, winding fatigue, magnet degradation, or overheating.

• Contaminants (water, debris) or corrosion can degrade motor internals.

• Mechanical stress, overloading, or torque spikes can accelerate wear.

• Loose connections or vibration can damage internal wiring.

• Overheating beyond specifications may cause insulation degradation.

Signs / early symptoms:

• Unusual noises (whining, grinding).

• Vibration or imbalance under load.

• Drop in efficiency, higher current draw for same power.

• Fault codes relating to motor or drive.

• Motor stall or hesitation.

Replacement / repair considerations:

• Check whether repair (rewinding bearings, replacing bearings) is feasible; sometimes it’s cheaper to replace the motor.

• Ensure matching motor parameters: voltage, power, torque, mounting, connectors.

• For replacement motors, check rotor design (interior magnet, permanent magnet, induction) and compatibility with inverter.

• Look for sealed designs or ingress protection rating (IP).

• Prefer motors with robust bearings, cooling, and known performance history.

• Rebalance if needed; align coupling and shaft tolerances carefully.

• Ensure alignment with motor controller (phase matching, wiring order).

4. High-Voltage Wiring, Connectors, and Cabling

Why it fails:

• High-voltage cables and connectors are exposed to heat, vibration, mechanical stress, and environmental exposure.

• Insulation degradation over time (especially under thermal cycling) can lead to breakdown or short circuits.

• Connector pins may corrode or become loose, increasing resistance or causing open circuits.

• Incorrect routing or mechanical stress can pinch or wear insulation.

• Aging or heat exposure may cause insulation to become brittle or crack.

Signs / early symptoms:

• High-voltage fault codes or disconnection errors.

• Arcing, smell of ozone, burning odor in severe cases.

• Increased resistance, voltage drop, or heating at connectors.

• Intermittent loss of power or dropouts.

• Visible damage or wear to wiring insulation.

Replacement / repair considerations:

• Use high-voltage rated cables (correct insulation, voltage rating, gauge).

• Match connector types and pinouts exactly (MV connectors, HV plugs).

• Use proper strain relief, routing, clamps, and shielding.

• Ensure all connectors are rated for temperature, vibration, and IP (ingress protection).

• Avoid reuse of worn connector parts; opt for new, matched parts.

• Use shielding, shielding drains, and grounding as required.

• Double-check insulation integrity, continuity, and dielectric testing after installation.

5. Charging System Components (Onboard Charger, Port, Cables)

Why it fails:

• The onboard charger (OBC) is an AC-to-DC converter that can fail due to electronics stress, overvoltage, cooling issues, or component wear.

• Charging ports (connectors, sockets) may wear, corrode, or develop poor contacts.

• Charging cable connectors can bend pins or degrade over time.

• Software or firmware issues controlling charging may cause failures or inconsistencies.

• Overheating or surges from charging station side can damage OBC.

Signs / early symptoms:

• Charging does not start or stops mid-cycle.

• Error codes referencing charger or port.

• Inconsistent charging current or voltage.

• Excess heat at charger housing or port.

• Visual corrosion or damage at port pins.

Replacement / repair considerations:

• Replacement should match voltage, current rating, communication protocol (e.g., CCS, CHAdeMO, etc.).

• Ensure thermal design is compatible (cooling, heat sinks).

• Use OEM or trusted high-quality aftermarket chargers/ports.

• Inspect connectors for wear, contact resistance, and corrosion; replace if needed.

• If firmware is involved, ensure compatibility.

• For portable cables, use cables rated for expected current and environmental conditions.

• Always follow safety guidelines and adhere to manufacturer spec for wiring.

6. Thermal Management & Cooling Systems

Why it fails:

• Many EV components (battery, inverter, motors) rely on liquid cooling or thermal conduction systems.

• Cooling hoses, pumps, junctions, radiators, valves, and sensors are subject to wear, leaks, blockage, or corrosion.

• Over time, coolant can degrade, or cooling circuits clog.

• Failure of a pump or sensor can cause overheating, which cascades damage into battery or electronics.

• Thermal expansion / contraction cycles stress connections, seals, and joints.

Signs / early symptoms:

• Overheating warnings, reduced performance.

• Elevated temperatures in battery, inverter, or motor.

• Coolant leaks, drops in coolant level.

• Uneven temperature distribution among modules.

• Strange noises from pumps or valves, or no flow indication.

Replacement / repair considerations:

• Use compatible coolant types (nonconductive, suitable for EV systems).

• Replace hoses, pumps, sensors with equivalent or better spec parts (pressure, temperature rating).

• Ensure proper flow paths, venting, and bleed systems.

• Retain or upgrade thermal sensors and monitoring systems.

• Inspect and clean radiators, heat exchangers; ensure they are free of blockages.

• Recalibrate thermal control when adding new components.

7. Low-Voltage / Auxiliary Electrical System

Why it fails:

• EV trucks still have a 12 V (or similar) auxiliary system that powers lights, infotainment, controls, actuators.

• That system is prone to common electrical failures: blown fuses, bad relays, wiring faults, bad ground connections.

• Accessories, control modules, or loads may overdraw the 12V system, stressing wiring or battery.

• Inadequate design or poor maintenance can accelerate failure.

Signs / early symptoms:

• Loss of lights, dashboard functions, windows, or accessories.

• Blown fuses, or error codes referencing auxiliary circuits.

• Voltage drops or instability in 12V system.

• Intermittent failures of auxiliary circuits.

Replacement / repair considerations:

• Use correct gauge wire, fuse ratings, relays, connectors.

• Replace aged wiring harness segments or connectors.

• Use high-quality, automotive-grade components resistant to vibration, heat, moisture.

• Ensure proper grounding and bonding.

• If upgrades add load, size the wiring or battery accordingly.

8. Suspension, Chassis, & Wear Items

Though not unique to EVs, these mechanical systems still fail and sometimes more aggressively in EVs due to extra weight and torque.

Why it fails:

• EV trucks usually carry heavy battery packs, increasing load on suspension, bushings, bearings, mounts, and ball joints.

• Torque delivery can stress driveline mounts or joints.

• Road shocks, vibrations, and road conditions wear components.

• Misalignment or harsh use accelerates wear.

Signs / early symptoms:

• Uneven tire wear, vibrations, rattles, or clunks.

• Steering pull or drift.

• Loose suspension, play in joints.

• Noises when going over bumps or under load.

Replacement / repair considerations:

• Use parts rated for higher load, higher torque.

• Prefer OEM or heavy-duty aftermarket parts.

• Replace in matched sets (e.g., both sides) when possible to retain balance.

• Use correct torque settings, alignment, and mounting points.

• Inspect related components (bushings, mounts, fasteners) when replacing.

9. Sensors, Control Modules & Software

Why it fails:

• EV trucks have many sensors (temperature, current, voltage, position), control modules, and communication networks (CAN, LIN).

• Software bugs, firmware glitches, or module failures can manifest as parts failure.

• Harsh environments (heat, moisture, vibration) can degrade electronic modules or connectors.

• ESD or voltage transients can damage sensitive electronics.

Signs / early symptoms:

• Fault codes, warning lights, or "limp" modes.

• Unexpected behavior: reduced power, incorrect readings, system disablements.

• Module resets, communication errors or disconnects.

• Inconsistent sensor values.

Replacement / repair considerations:

• Use modules matching the same firmware or compatible versions.

• If reprogramming is needed, ensure proper tools or dealer-level calibration.

• Match communication protocols, harness pinouts, and power/ground references.

• Ensure sensors are rated for temperature, vibration, and environment.

• After installation, calibrate or relearn modules or sensors if required.

10. Safety Systems: Fuses, Disconnects, Contactors, Relays

Why it fails:

• These devices are essential for isolating high voltage, protecting circuits, and enabling safe maintenance.

• Contactors may stick or fail under frequent switching.

• Fuses blow under overcurrent; fuse holders or links can corrode.

• HV disconnect switches may fail due to wear or mechanical issues.

• Relays and safety interlocks can fail electrically or mechanically.

Signs / early symptoms:

• Inability to energize the high-voltage system.

• Safety interlock or diagnostic error codes.

• Contactors that don’t engage or drop out.

• Blown fuses or fuse link failures.

• Intermittent power cutouts when load changes.

Replacement / repair considerations:

• Use properly rated HV contactors, fuses, relays with matching specifications (current, voltage, durability).

• Replace worn contacts or mechanical parts proactively.

• Ensure proper control wiring and signal compatibility.

• Use genuine or high-grade parts designed for EV service.

• Test new parts under load conditions.

• Follow safety protocols: ensure system is de-energized, isolation, and proper procedures when working with HV.

How to Choose Replacement Parts: A Practical Guide

Knowing the failure modes is only half the battle. The more critical part is choosing the right replacement parts so you don’t repeat problems. Below is a comprehensive checklist and strategy for sourcing and selecting parts for EV trucks.

1. Know the Exact Specifications & OEM Part Numbers

• Always begin with the OEM part number or specification sheet.

• Match voltage, current, power, mechanical mounting, cooling, and communications interfaces.

• Don’t rely purely on generic descriptions – small differences matter (e.g. pin layout, wiring length).

• Check any revisions or version differences (e.g. firmware, connector updates).

2. OEM vs Aftermarket vs Remanufactured / Refurbished

• OEM (Original Equipment Manufacturer): highest compatibility, warranty support, and reliability, but also higher cost.

• Aftermarket high-quality: provide cost advantage but ensure they meet or exceed OEM specs.

• Refurbished / remanufactured parts: can be cost-effective for battery modules, motors, etc., but require verification of quality, testing, and warranty.

• Avoid cheap or unbranded parts with no track record, especially for critical systems.

3. Quality & Certification

• Look for safety certifications (UL, CE, IEC), especially for power electronics and HV parts.

• Ensure parts conform to automotive standards (ISO 26262, AEC-Q100, etc. where applicable).

• Check third-party test reports, reviews, or references from users in EV context.

• Prefer components with stress ratings (temperature, vibration, shock).

4. Thermal & Cooling Compatibility

• Replacement parts must integrate properly into existing thermal/cooling designs.

• Check whether cooling ports, coolant flow, sensors, and temperature limits match.

• If the new part runs hotter, ensure that cooling is adequate; upgrading cooling may be necessary.

5. Electrical Interface & Communications

• Ensure connectors, pinouts, CAN or other communications protocols match the vehicle’s system.

• Power supply, grounding, signal isolation must be compatible.

• Ensure safeguards (e.g. voltage surges, EMI protection) are built into the part.

6. Mechanical Fit & Robustness

• Check mounting dimensions, torque requirements, vibration tolerances.

• Consider ingress protection (IP ratings) for water/dust.

• Use appropriate gaskets, O-rings, and sealing components.

7. Testing, Validation & Calibration

• After install, components should be tested under load, with thermal monitoring.

• Calibration or relearning (e.g. BMS balancing, motor alignment, ECU pairing) is often required.

• Verify correct behavior, error codes, and ensure there is no unintended interaction.

8. Warranty, Support & Documentation

• Strong warranty (1 year, 2 years, etc.) helps mitigate risk.

• Good technical support, documentation, wiring diagrams, and installation instructions are valuable.

• Suppliers who back their parts with support are better partners for long-term reliability.

9. Supply Chain & Availability

• Because EV components are somewhat specialized, lead times may be long.

• Favor vendors with consistent stock, reliable shipping, and good logistics.

• Keep critical spares (e.g. contactor, fuse, connectors) on hand for quick replacement.

10. Cost vs Lifecycle Trade-off

• Sometimes paying more up front for a premium component saves money over the life of the truck (less downtime, fewer failures).

• Avoid “cheaper now, broken soon” mentality, especially for safety or HV parts.

• Balance cost, reliability, warranty, and downtime risk.

Frequently Asked Questions 

Here are common questions people ask, and concise, accurate answers:

Which part fails most often in EV trucks?

The battery pack and battery management system (BMS) tend to be the most critical and costly components under stress. High-voltage wiring & connectors, charging hardware (onboard charger), and thermal systems are also common failure points.

Can I replace one battery module instead of the full pack?

Yes, if the battery pack is modular in design (divided into modules), replacing only the damaged module is often feasible and cost-effective. However, you must ensure the new module matches the pack’s chemistry, voltage, capacity, and BMS integration.

Should I always use OEM parts?

OEM parts are safest in terms of compatibility and warranty. But high-quality aftermarket or remanufactured parts can be used, provided you verify specs, quality, warranty, and compatibility. Avoid generic parts with no track record, especially for safety or HV systems.

How can I tell if a replacement inverter or motor is compatible?

You must compare voltage, current rating, mechanical interfaces, connectors, cooling requirements, control protocols, and software compatibility. Checking part numbers, wiring diagrams, and vendor support is essential.

How do I test that a new part is working correctly?

Run diagnostics under load, monitor temperatures, voltage, and current. Look for error codes or warnings. Test the system across operational range (cold, hot, varying loads). After installation, perform calibrations or relearn steps as necessary.

What safety precautions should I take when working on EV parts?

Always de-energize the high-voltage system, isolate the battery, follow manufacturer safety procedures, use insulated tools, wear protective gloves and gear, and ensure interlock or safety systems are disabled per instructions. Only qualified personnel should work on HV components.

When should I replace the contactors or fuses proactively?

As a preventative measure, inspect them periodically. Replace them if signs of wear, arcing, pitting, or mechanical degradation are present, especially if the truck is used under heavy load or frequent cycling.

How important is thermal management in EV trucks?

Extremely important. Poor cooling can accelerate degradation of battery, inverter, motor, or electronics. Replacement parts must match or improve thermal design, using proper coolant, sensors, and flow management.

What happens if a connector fails under load?

A bad connector can raise resistance, produce heat, or lead to voltage drop or disconnections. In high-voltage circuits, this can be dangerous—leading to arcing or cascading failures. Always monitor and replace worn connectors promptly.

Are software or firmware updates a cause of failures?

Yes. Incompatibilities, bugs, or firmware mismatches may disable systems, misinterpret sensor data, or prevent modules from communicating. Always use the correct firmware version and test thoroughly after upgrades.

Conclusion

Electric truck technology is evolving rapidly, and while EVs tend to have fewer mechanical parts than traditional trucks, their electrical and thermal systems bring new and critical points of failure. Understanding how and why components fail helps you choose better replacement parts, avoid repeated breakdowns, and make smart investments in quality, compatibility, and support.

When sourcing replacement parts, always prioritize correct specifications, safety ratings, compatibility, good documentation, and warranty. Whether you rely on OEM, trusted aftermarket, or remanufactured options, rigorous testing and calibration after installation is key.

For buyers, fleet operators, repair shops, and DIYers operating in the U.S. in 2025 and beyond, getting this right means fewer surprises, safer trucks, and better return on investment.

If you like, I can turn this into a downloadable PDF, add diagrams, or prepare a shorter version for blog or newsletter use. Do you want me to refine further (or localize it to specific EV truck brands)?