The JLG 600AJ aerial lift features a comprehensive instrument cluster with warning and indicator lights to ensure safe operation. Understanding these symbols is critical for preventing damage and avoiding downtime on the job site.
JLG 600AJ Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical fault has been detected that requires immediate shutdown of the JLG 600AJ engine and hydraulic system to prevent damage or injury. | Stop all motion, turn off engine, and consult the operator's manual or contact service. | |
| Master Caution | AMBER | A non-critical fault exists that may affect performance; on the 600AJ, this often relates to hydraulic oil temperature or engine air filter restriction. | Check the display for specific fault codes and address the issue promptly. | |
| Engine Oil Pressure | RED | Engine oil pressure is below safe limits, risking severe engine damage on the JLG 600AJ's diesel powerplant. | Shut off engine immediately and check oil level and pressure switch. | |
| Battery / Charging | RED | The 600AJ's charging system is not producing sufficient voltage to maintain battery charge, often due to a failed alternator or loose belt. | Check alternator drive belt and electrical connections; run engine at low load until repaired. | |
| Coolant Temperature | RED | Engine coolant temperature has exceeded the safe operating range for the 600AJ's diesel engine, risking overheating and gasket failure. | Reduce engine load, allow to cool, and inspect coolant level and radiator fins. | |
| Hydraulic System | AMBER | Hydraulic oil temperature or pressure is abnormal, which can reduce lift performance and damage seals on the 600AJ boom. | Check hydraulic fluid level, cooler, and for external leaks before continuing work. | |
| Low Fuel | AMBER | The 600AJ's diesel fuel level is low and requires refueling soon to avoid engine air ingestion during operation. | Refuel with diesel as soon as possible; do not run out of fuel. | |
| Parking Brake | RED | Parking brake is engaged or a fault exists in the brake system; on the 600AJ, this lamp illuminates red when the brake is applied and flashes if a malfunction is detected. | If flashing, release and reapply; if stays on, inspect brake linkage and switches. | |
| Fasten Seat Belt | RED | The operator's seat belt is not buckled; the 600AJ requires the belt to be fastened to enable boom movement. | Fasten seat belt securely before operating. | |
| Work Lights | GREEN | Work lights are turned on, illuminating the work area around the 600AJ for improved visibility in low-light conditions. | No action needed; turn off when not required to save battery. | |
| Beacon / Rotating Light | GREEN | The rotating beacon is activated to warn personnel of the 600AJ's presence on the job site. | Ensure beacon is on when machine is in operation; turn off when parked. | |
| Glow Plug / Preheat | AMBER | Engine glow plugs are preheating for cold start; wait until the light turns off before cranking the 600AJ's diesel engine. | Turn key to ON position and wait for light to extinguish, then start engine. | |
| Air Filter Restriction | AMBER | The engine air intake filter is clogged, restricting airflow and reducing power on the 600AJ. | Check and replace air filter element; inspect for debris in intake path. | |
| Low Oil Level | AMBER | Engine oil level is below the safe minimum; on the 600AJ this could lead to oil starvation and rapid wear. | Check oil dipstick and add oil to full mark; inspect for leaks. |
14 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 oil level
- Faulty oil pressure switch
- Worn oil pump or bearings
What to do
Immediately shut down the 600AJ engine. Check oil level and top up if low. If light persists, do not operate; tow to service for pressure diagnosis.
Hydraulic System Overheat
Common causes
- Low hydraulic fluid
- Clogged cooler fins
- Continuous high-demand operation
What to do
Allow the JLG 600AJ to idle with hydraulics in neutral to cool down. Check fluid level and clean cooler fins. Avoid prolonged heavy lifting without breaks.
Engine Coolant Overheat
Common causes
- Low coolant level
- Radiator blockage
- Failed thermostat or water pump
What to do
Stop the 600AJ and let engine cool. Check coolant reservoir and radiator for debris. Do not open hot cap; add coolant if safe. If recurring, inspect thermostat and water pump.
Battery Charging Failure
Common causes
- Loose or broken alternator belt
- Failed alternator
- Corroded battery terminals
What to do
Check alternator belt tension and condition on the 600AJ. Inspect battery connections for corrosion. If light stays on, replace alternator.
Master Warning (Stop) Light
Common causes
- Any critical fault (oil, coolant, charging)
- Engine overspeed
- Hydraulic pressure loss
What to do
The 600AJ will automatically limit functions. Turn off engine, note the other warning lights, and address the root cause. Do not resume operation until resolved.
Frequently Asked Questions
What does the amber Master Caution light mean on my JLG 600AJ?
It indicates a system advisory that doesn't require immediate stop but needs attention, such as a hydraulic oil temperature rise or air filter restriction. Check the display for codes.
Why does my parking brake light flash while driving the 600AJ?
A flashing red parking brake light signals a brake system fault—possibly a switch misalignment or low fluid. Stop and release/reapply the brake; if it persists, inspect the brake linkage.
The glow plug light stays on longer than usual; is that normal?
In cold conditions, the preheat cycle may extend on the 600AJ. However, if it stays on for more than 15 seconds without starting, the glow plugs or relay may be failing—have them tested.
My battery light came on but the engine runs fine. Should I worry?
Yes—the battery light indicates the 600AJ's alternator is not charging. You have limited runtime before the battery drains. Check belt tension and alternator output as soon as possible.
How do I know if the hydraulic system light is serious?
The amber hydraulic light on the 600AJ warns of high temperature or low pressure. If it stays on, stop and let the system cool; check fluid level. Operating with this light may damage pumps and seals.
Can I override the seat belt interlock on the 600AJ?
No—the seat belt must be fastened for boom and drive functions to operate. Do not bypass this safety feature; it is critical for operator protection in the event of a tip-over.