08-28-2025, 02:00 AM
Bobcat 773 Overview and Control System Evolution
The Bobcat 773 skid steer loader was introduced in the late 1990s as part of Bobcat’s 700-series, designed for mid-range lifting and hydraulic performance. With a rated operating capacity of 1,750 lbs and a 46-horsepower Kubota diesel engine, the 773 became a staple in landscaping, construction, and agricultural work. One of its notable features was the introduction of Advanced Hand Controls (AHC), an electronic joystick system that replaced traditional mechanical linkages and foot pedals.
While AHC offered smoother control and reduced operator fatigue, it also introduced a layer of electronic complexity that could become problematic over time—especially in harsh environments or machines with high operating hours.
Symptoms of Lift and Tilt Malfunction
Operators have reported a recurring issue where the lift and tilt functions on the 773 suddenly stop responding. The machine may operate normally for hours, then abruptly lose bucket control. Common symptoms include:
Terminology Clarification
Machines operating near saltwater or in humid climates—such as coastal Hawaii or snowy regions like Alaska—are prone to electrical corrosion. Even if terminals appear clean, microscopic oxidation can increase resistance and disrupt voltage signals. In some cases, adding moisture (e.g., spraying water) temporarily restores conductivity, which explains the weather-dependent behavior.
Preventive steps include:
Several components may contribute to intermittent lift/tilt failure:
Field Anecdotes and Operator Insights
A technician in Wisconsin noted that salt-laden air combined with dry connectors can cause high resistance, preventing proper voltage delivery. Cleaning and sealing all terminals resolved similar issues on a 773 used for snow removal.
Another operator in Missouri discovered two unused leads buried in mud behind the side panels. Cleaning and reconnecting these reduced error frequency dramatically. These leads may be part of the interlock or sensor system and are often overlooked during routine service.
In Alabama, a user with a hand-and-foot control model resolved the issue by replacing the BICS solenoid and stem, restoring full function without replacing the computer.
Hydraulic Behavior and Pressure Drop
Lowering the boom requires minimal hydraulic pressure, which can cause system pressure to drop near zero. If the check valve fails to trap oil across the BICS solenoid, lock valves may engage prematurely, disabling lift and tilt. This scenario explains why the machine fails during lowering but not during lifting or tilting under load.
Recommendations:
Intermittent lift and tilt failures in the Bobcat 773 with AHC controls are often the result of electrical corrosion, solenoid malfunction, or pressure instability in the hydraulic circuit. While replacing the AHC computer may seem like a solution, deeper inspection of connectors, check valves, and solenoids is often more effective. In coastal or high-humidity environments, proactive electrical maintenance is essential to preserve machine reliability. With careful diagnosis and attention to component-level behavior, even the most temperamental 773 can be brought back to consistent performance.
The Bobcat 773 skid steer loader was introduced in the late 1990s as part of Bobcat’s 700-series, designed for mid-range lifting and hydraulic performance. With a rated operating capacity of 1,750 lbs and a 46-horsepower Kubota diesel engine, the 773 became a staple in landscaping, construction, and agricultural work. One of its notable features was the introduction of Advanced Hand Controls (AHC), an electronic joystick system that replaced traditional mechanical linkages and foot pedals.
While AHC offered smoother control and reduced operator fatigue, it also introduced a layer of electronic complexity that could become problematic over time—especially in harsh environments or machines with high operating hours.
Symptoms of Lift and Tilt Malfunction
Operators have reported a recurring issue where the lift and tilt functions on the 773 suddenly stop responding. The machine may operate normally for hours, then abruptly lose bucket control. Common symptoms include:
- No response when attempting to lower or tilt the bucket
- Functions restored only after restarting the machine
- Error lights behaving inconsistently—left light never illuminates, right light flashes intermittently
- Failures more frequent in hot, dry weather; improved performance in cooler, damp conditions
- Spraying water on the interlock computer temporarily restores function
Terminology Clarification
- AHC (Advanced Hand Controls): Electronic joystick system controlling lift, tilt, and drive functions.
- BICS (Bobcat Interlock Control System): Safety system that prevents lift and tilt unless certain conditions are met (e.g., seat occupied, seat bar down).
- Solenoid Valve: Electrically actuated valve that directs hydraulic flow to specific functions.
- Check Valve: Hydraulic component that maintains pressure and prevents backflow, critical during low-pressure operations like lowering the boom.
Machines operating near saltwater or in humid climates—such as coastal Hawaii or snowy regions like Alaska—are prone to electrical corrosion. Even if terminals appear clean, microscopic oxidation can increase resistance and disrupt voltage signals. In some cases, adding moisture (e.g., spraying water) temporarily restores conductivity, which explains the weather-dependent behavior.
Preventive steps include:
- Disassembling and cleaning all connectors with contact cleaner
- Applying dielectric grease to prevent future corrosion
- Inspecting harnesses for pinched or rubbed wires, especially near the fuse panel and under the cab
Several components may contribute to intermittent lift/tilt failure:
- AHC Joystick Switches: Swapping plugs between joysticks can help isolate faulty switches.
- BICS Solenoid and Stem: Located on the control valve body, failure here can prevent hydraulic flow to lift/tilt cylinders.
- Check Valve Screens: Clogged screens near the BICS solenoid can trap debris and block pressure.
- Interlock Computer: Suspected to be the root cause in many cases, especially when error lights behave erratically.
Field Anecdotes and Operator Insights
A technician in Wisconsin noted that salt-laden air combined with dry connectors can cause high resistance, preventing proper voltage delivery. Cleaning and sealing all terminals resolved similar issues on a 773 used for snow removal.
Another operator in Missouri discovered two unused leads buried in mud behind the side panels. Cleaning and reconnecting these reduced error frequency dramatically. These leads may be part of the interlock or sensor system and are often overlooked during routine service.
In Alabama, a user with a hand-and-foot control model resolved the issue by replacing the BICS solenoid and stem, restoring full function without replacing the computer.
Hydraulic Behavior and Pressure Drop
Lowering the boom requires minimal hydraulic pressure, which can cause system pressure to drop near zero. If the check valve fails to trap oil across the BICS solenoid, lock valves may engage prematurely, disabling lift and tilt. This scenario explains why the machine fails during lowering but not during lifting or tilting under load.
Recommendations:
- Inspect and clean the check valve and associated screens
- Verify that the BICS solenoid receives consistent voltage
- Monitor system pressure during boom lowering to confirm valve behavior
Intermittent lift and tilt failures in the Bobcat 773 with AHC controls are often the result of electrical corrosion, solenoid malfunction, or pressure instability in the hydraulic circuit. While replacing the AHC computer may seem like a solution, deeper inspection of connectors, check valves, and solenoids is often more effective. In coastal or high-humidity environments, proactive electrical maintenance is essential to preserve machine reliability. With careful diagnosis and attention to component-level behavior, even the most temperamental 773 can be brought back to consistent performance.
