Troubleshooting Electronic Governor Issues on the Marklift CH60C Boom Lift

[MikePhua]

The Marklift Legacy and CH60C Model Overview
Marklift was a prominent manufacturer of aerial work platforms during the 1980s and 1990s, producing a range of scissor lifts and boom lifts for industrial and construction use. The CH60C is a telescopic boom lift designed for high-reach applications, offering approximately 60 feet of vertical lift and horizontal outreach suitable for steel erection, maintenance, and signage installation. Though the company ceased operations decades ago, many CH60C units remain in service, especially in rental fleets and privately maintained yards.
The CH60C is powered by an internal combustion engine, typically gasoline or diesel, and uses an electronic governor to regulate engine speed based on hydraulic demand and operator input. This system ensures consistent RPM during lift and drive operations, preventing stalling and maintaining hydraulic pressure.
Terminology annotation:
- Electronic Governor: A control module that adjusts engine throttle electronically to maintain target RPM under varying loads.
- Hydraulic Drive: A propulsion system using pressurized fluid to power wheel motors or actuators.
- Boom Function: The extension, retraction, and rotation of the lift arm controlled via hydraulic valves.
- Service Manual: A technical document detailing diagnostic procedures, wiring diagrams, and component specifications.
Symptoms of Governor Malfunction During Movement
Operators have reported that the CH60C runs normally when stationary but stalls or shuts down when attempting to drive or operate the boom. This behavior typically points to a fault in the electronic governor system, which fails to increase engine RPM in response to hydraulic load. As a result, the engine bogs down and may shut off due to low idle speed.
Common symptoms include:

• Engine idling fine but stalling during drive or lift
  
• No audible increase in RPM when hydraulic functions are engaged
  
• Intermittent operation depending on ambient temperature or vibration
  
• Lack of response from throttle actuator or solenoid
  

In one case, the lift would start and idle but immediately shut off when the drive joystick was moved. This indicated that the governor was not compensating for the hydraulic load, causing the engine to stall under pressure.
Diagnosing the Electronic Governor System
The electronic governor consists of several components: a control module, throttle actuator, position sensor, and input signals from the hydraulic system. Diagnosing the issue requires a step-by-step approach using a multimeter and visual inspection.
Diagnostic steps:

• Check battery voltage and ground connections to the governor module
  
• Inspect wiring harness for corrosion, loose terminals, or abrasion
  
• Test throttle actuator response by manually engaging hydraulic functions
  
• Verify input signal from hydraulic pressure switch or load sensor
  
• Consult the service manual for pinout and voltage ranges
  

If the actuator fails to respond, it may be seized or disconnected. If the module receives no signal from the hydraulic system, it won’t trigger RPM increase. In older machines, vibration and heat can degrade solder joints or cause intermittent faults.
Repair Strategies and Replacement Options
Repairing the governor system may involve replacing individual components or retrofitting a manual throttle override. Since Marklift is no longer in business, sourcing OEM parts can be difficult. However, many components are generic and can be matched by specification.
Repair suggestions:

• Replace throttle actuator with a compatible unit from another lift brand
  
• Install a manual cable throttle as a temporary workaround
  
• Use a universal governor module with adjustable parameters
  
• Rewire corroded harness sections with marine-grade connectors
  
• Mount components on vibration-dampened brackets to reduce wear
  

One technician successfully retrofitted a Genie-brand actuator onto a CH60C using a custom bracket and splice harness. The lift resumed full function with improved throttle response.
Preventative Maintenance and Long-Term Reliability
To prevent future failures, regular inspection and cleaning of the governor system is essential. Dust, moisture, and vibration are the primary enemies of electronic control systems in outdoor equipment.
Maintenance tips:

• Clean connectors with contact cleaner every 6 months
  
• Secure wiring with zip ties and protective loom
  
• Check throttle linkage for binding or wear
  
• Test governor response during pre-shift inspections
  
• Keep a printed copy of the service manual onboard
  

In one fleet, implementing a quarterly electrical inspection reduced electronic faults by 70% across all boom lifts. Operators were trained to recognize early signs of governor lag and report them before full failure occurred.
Conclusion
The Marklift CH60C remains a capable and valuable boom lift despite its age, but electronic governor issues can compromise its reliability during movement. By understanding the system’s components, diagnosing faults methodically, and applying creative repair strategies, operators can restore full functionality and extend the life of this legacy machine. In the world of aerial work platforms, precision and uptime matter—and even a decades-old lift can still rise to the occasion with the right care.