JCB Telehandler Ignition Stays On After Key Is Removed

[MikePhua]

JCB’s Telehandler Line and Electrical System Design
JCB (Joseph Cyril Bamford Excavators Ltd.), founded in 1945 in Staffordshire, England, is one of the world’s leading manufacturers of construction and agricultural equipment. Its telehandlers—also known as Loadalls—have become a global standard for lifting, stacking, and material handling in tight spaces. By the mid-2010s, JCB had sold over 250,000 telehandlers worldwide, with models ranging from compact 5-meter reach units to heavy-duty 20-meter machines.
JCB telehandlers are equipped with advanced electrical systems that integrate ignition control, safety interlocks, hydraulic lockouts, and CAN-bus communication. These systems are designed to ensure safe operation and prevent unintended movement or power draw when the machine is shut down.
Symptoms of Ignition Staying On After Key Removal
Operators have reported a fault where the ignition circuit remains active even after the key is turned off and removed. This can lead to:

• Dashboard lights staying illuminated
  
• Hydraulic lockout solenoids remaining energized
  
• Audible alarms or buzzers continuing to sound
  
• Battery drain overnight
  
• Inability to reset fault codes or initiate diagnostics
  

In one rental fleet in Alberta, a JCB 535-95 telehandler exhibited this issue repeatedly. Technicians found that the ignition relay was sticking due to internal arcing, causing the circuit to remain closed even without key input.
Root Causes and Diagnostic Path
This fault typically stems from one or more of the following:

• Stuck ignition relay due to worn contacts or coil failure
  
• Short circuit in the ignition switch wiring harness
  
• Faulty diode in the relay suppression circuit
  
• CAN-bus communication error causing logic lockup
  
• Moisture ingress into fuse box or relay panel
  
• Ground loop or backfeed from auxiliary circuits
  

Recommended diagnostic steps:

• Disconnect battery and inspect ignition relay for heat damage or corrosion
  
• Use a multimeter to test continuity across relay terminals with key removed
  
• Check ignition switch wiring for frayed insulation or pinched conductors
  
• Inspect fuse box for signs of moisture, oxidation, or loose terminals
  
• Scan ECU for fault codes related to ignition or power management
  
• Verify that auxiliary circuits (e.g., beacon lights, radio) are not backfeeding voltage
  

In one case in New Zealand, a telehandler used in coastal construction had salt corrosion inside the relay panel. After cleaning and sealing the panel, the ignition fault disappeared.
Terminology Notes

• Ignition Relay: An electromechanical switch that controls power to the ignition circuit, activated by the key switch.
  
• CAN-bus: A Controller Area Network protocol used for communication between electronic control units.
  
• Backfeed: Unintended electrical current flowing in reverse through a circuit, often due to wiring faults.
  
• Ground Loop: A condition where multiple ground paths create voltage differences, causing erratic behavior.
  
• Suppression Diode: A diode used to prevent voltage spikes when a relay coil is de-energized.
  

Preventive Measures and Component Upgrades
To prevent ignition faults:

• Replace ignition relays every 2,000 hours or during major service
  
• Use sealed relays rated for high vibration and moisture environments
  
• Apply dielectric grease to relay terminals and fuse contacts
  
• Install moisture barriers or desiccant packs in electrical enclosures
  
• Route wiring harnesses away from hydraulic lines and heat sources
  
• Perform ECU resets after electrical repairs to clear logic faults
  

In one fleet in Texas, upgrading to solid-state ignition relays and adding a secondary ground strap reduced electrical faults by 60% and improved cold-start reliability.
Operator Experience and Field Adaptations
Operators dealing with ignition faults often resort to temporary fixes:

• Disconnecting battery overnight to prevent drain
  
• Tapping relay housing to release stuck contacts
  
• Installing manual kill switches to isolate ignition circuit
  
• Labeling fuse box and relay panel for faster troubleshooting
  

While these workarounds may restore function short-term, they can mask deeper issues and compromise safety systems. Permanent solutions require proper diagnostics and component replacement.
Final Thoughts
An ignition circuit that remains active after key removal is more than an electrical nuisance—it’s a potential safety hazard and a drain on operational efficiency. In JCB telehandlers, the fault often lies in relay behavior, wiring integrity, or moisture intrusion. With methodical inspection and preventive upgrades, this issue can be resolved and avoided in future deployments. In the world of material handling, power should respond to the key—not linger after it’s gone.