The Komatsu PC78 is a compact hydraulic excavator widely used in urban construction and utility work. Its instrument cluster provides operators with essential alerts to ensure reliable performance and machine protection. Understanding these indicators is key to safe and efficient operation of the PC78.
Komatsu PC78 Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical fault has been detected in the Komatsu PC78, potentially risking severe damage or unsafe operation. | Safely park and shut down the machine immediately; consult the display for detailed fault information. | |
| Master Caution | AMBER | A non-critical issue has been identified that could affect the PC78’s performance or longevity if unaddressed. | Review the monitor panel for further details and schedule necessary maintenance soon. | |
| Check Engine (MIL) | AMBER | The engine management system has detected an abnormality specific to the PC78’s diesel engine. | Continue operation with caution and arrange for diagnostic service at the earliest opportunity. | |
| Engine Oil Pressure | RED | Engine oil pressure has dropped below safe levels, risking severe engine damage in the PC78. | Stop the engine immediately and check oil level and possible leaks before restarting. | |
| Battery / Charging | RED | The alternator is not charging the battery, risking loss of electrical power on the PC78. | Inspect the alternator belt and electrical connections before resuming work. | |
| Coolant Temperature | RED | Engine coolant temperature has reached a critical high, threatening engine overheating in the PC78. | Shut down the engine to allow cooling, then inspect coolant level and radiator for blockages. | |
| Hydraulic System | AMBER | A hydraulic system malfunction or abnormal pressure has been detected in the PC78. | Check for hydraulic leaks, abnormal noises, or sluggish operation; arrange service if needed. | |
| Hydraulic Oil | AMBER | Hydraulic oil level or quality is below recommended limits for safe PC78 operation. | Top up hydraulic oil and inspect for leaks or contamination. | |
| Low Fuel | AMBER | Fuel level is low and the PC78 may soon run out of diesel if not refueled. | Refuel at the next convenient opportunity to avoid work interruption. | |
| DEF / AdBlue | AMBER | The DEF (AdBlue) level is low or there is a malfunction in the emission control system on the PC78. | Refill the DEF tank and check for any system errors to maintain compliance and performance. | |
| DPF / Regeneration | AMBER | Diesel Particulate Filter is full and regeneration is required to prevent engine power loss in the PC78. | Initiate DPF regeneration per the operator’s manual, or drive at higher RPMs if safe. | |
| Water in Fuel | AMBER | Water contamination has been detected in the fuel system, risking injector damage on the PC78. | Drain the water separator as soon as possible to protect the fuel system. | |
| Fuel Filter / Water Separator | AMBER | The fuel filter is clogged or the water separator needs servicing on the PC78. | Replace the filter or drain the separator to ensure proper fuel flow. | |
| Engine Oil Temperature | RED | Engine oil temperature is excessively high, risking lubrication breakdown in the PC78. | Stop the engine and allow it to cool; check oil level and cooling system. | |
| Air Filter | AMBER | The air filter is clogged, which can reduce engine performance on the PC78. | Inspect and clean or replace the air filter element. | |
| Service / Hour Meter | AMBER | Scheduled maintenance interval has been reached based on PC78 operating hours. | Complete the recommended service tasks as indicated in the maintenance schedule. | |
| Work Lights | GREEN | Work lights are switched on, providing illumination for PC78 operation in low light. | No action needed unless lights are not required; switch off when done. | |
| Beacon / Rotating Light | AMBER | The beacon is active, signaling the PC78’s presence for site safety. | No action needed unless beacon use is unnecessary. | |
| Swing / Slew Lock | AMBER | Swing lock is engaged, restricting the PC78’s upper structure rotation. | Disengage the swing lock before attempting to rotate the upper structure. | |
| Overload / Capacity | RED | The PC78’s lifting load exceeds safe capacity, risking machine stability. | Lower the load immediately and reassess lifting procedures. | |
| Door Open | AMBER | A cab door is open on the PC78, which could be a safety hazard. | Ensure all cab doors are securely closed before moving the machine. |
21 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Engine Oil Pressure Warning
Common causes
- Low engine oil level
- Oil pump failure
- Oil filter blockage
What to do
Immediately stop the Komatsu PC78, check oil level and top up if low; inspect for leaks or oil filter issues, and contact a technician if the warning persists.
Coolant Temperature Warning
Common causes
- Low coolant level
- Radiator blockage
- Faulty thermostat or water pump
What to do
Shut down the PC78 to prevent overheating, inspect coolant level and radiator, and resolve any blockages or leaks before continuing work.
Overload Warning
Common causes
- Attempting to lift loads beyond rated capacity
- Incorrect use of lifting mode
- Improper attachment or load handling
What to do
Lower the load immediately, verify the weight and lifting configuration, and use proper lifting techniques as outlined in the PC78’s manual.
Hydraulic System Warning
Common causes
- Hydraulic fluid leakage
- Contaminated or low hydraulic oil
- Malfunctioning hydraulic pump
What to do
Inspect the PC78’s hydraulic system for visible leaks, check fluid levels and quality, and repair or replace components as necessary.
Battery / Charging Warning
Common causes
- Alternator malfunction
- Loose or corroded battery terminals
- Broken drive belt
What to do
Check battery terminals and alternator belt for damage or looseness; if unresolved, have the PC78’s charging system professionally inspected.
Frequently Asked Questions
What should I do if the DPF regeneration light stays on in my PC78?
If the DPF regeneration light remains lit, initiate a parked regeneration as described in the operator’s manual, and avoid shutting off the engine during the process.
Why does the hydraulic oil light turn on even after topping up the fluid?
Persistent hydraulic oil warnings may indicate a leak, a faulty sensor, or contamination—inspect the system closely and consult a Komatsu technician if the alert continues.
Is it safe to operate the PC78 with the master caution light on?
While the master caution is not as severe as a master warning, it signals a condition that should be checked soon to avoid performance issues or further damage.
How often should I service the air filter on the PC78?
Service intervals vary by environment, but replace or clean the air filter element whenever the indicator appears or during scheduled maintenance.
What does the swing lock indicator mean on the PC78?
The swing lock light shows that the upper structure’s rotation is locked; disengage it before rotating the house to prevent damage.
Can I continue working if the DEF/AdBlue light comes on?
You can finish the current task, but refill the DEF tank promptly to avoid engine derating or emission system faults.