The JLG 800AJ aerial lift features a comprehensive instrument cluster designed to keep operators informed of machine status and safety warnings. This guide explains each indicator light and provides specific actions for the 800AJ model.
JLG 800AJ Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical system fault has occurred on the JLG 800AJ, such as an engine or hydraulic failure, requiring immediate shutdown. | Stop the machine safely, turn off the engine, and consult the operator manual for fault codes. | |
| Master Caution | AMBER | A non-critical but important condition exists on the 800AJ, like a maintenance reminder or low fluid level. | Check the display for details and address the specific warning before continuing operation. | |
| Check Engine (MIL) | AMBER | The JLG 800AJ's engine control unit has detected a potential issue with emissions or engine performance. | Reduce load and have the engine diagnosed by a qualified technician as soon as possible. | |
| Engine Oil Pressure | RED | Engine oil pressure in the JLG 800AJ has dropped below safe operating levels, risking engine damage. | Immediately stop the engine and check oil level; do not restart until pressure is restored. | |
| Battery / Charging | RED | The JLG 800AJ's charging system is not supplying proper voltage, possibly due to a failed alternator or belt. | Continue only if necessary, but have the battery and alternator checked promptly to avoid breakdown. | |
| Coolant Temperature | RED | Engine coolant temperature on the 800AJ has exceeded safe limits, risking overheating and engine failure. | Stop the machine, let the engine cool, and check coolant level and radiator for blockages. | |
| Hydraulic System | AMBER | A hydraulic system issue, such as low fluid or a filter restriction, has been detected in the JLG 800AJ. | Check hydraulic fluid level and inspect for leaks; operate at reduced capacity until resolved. | |
| Overload / Capacity | RED | The JLG 800AJ has exceeded its rated platform capacity, triggering a safety shutdown of lift functions. | Remove excess load immediately to restore safe operation; never bypass overload sensors. | |
| Parking Brake | RED | The parking brake on the JLG 800AJ is engaged or a fault exists in the brake system. | Ensure parking brake is released before moving; if light stays on, inspect brake system. | |
| Seat Belt | RED | The operator's seat belt in the JLG 800AJ is not fastened, or the buckle sensor is faulted. | Fasten seat belt immediately to enable boom and drive functions. | |
| Low Fuel | AMBER | Fuel level in the JLG 800AJ is low; remaining range is limited. | Refuel at the nearest safe location to avoid engine shutdown. | |
| High Beam | BLUE | The high-beam headlights on the JLG 800AJ are activated. | Dim high beams when approaching other machines or personnel. | |
| Hydraulic Oil | AMBER | Hydraulic oil temperature is high or level is low in the JLG 800AJ system. | Reduce workload and allow hydraulics to cool; check oil level when safe. | |
| Service / Hour Meter | GREEN | The JLG 800AJ has reached a scheduled maintenance interval based on engine hours. | Perform required service as per the operator manual at the next convenient time. | |
| Glow Plug / Preheat | AMBER | The intake air preheat system is active on the JLG 800AJ to aid cold starting. | Wait for the light to turn off before cranking the engine. | |
| Water in Fuel | AMBER | Water has been detected in the fuel system of the JLG 800AJ, which can damage injectors. | Drain the fuel-water separator immediately and refuel from a clean source. | |
| Air Filter | AMBER | The engine air filter on the JLG 800AJ is restricted and requires cleaning or replacement. | Inspect and replace the air filter to maintain engine performance. |
17 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Engine Overheating
Common causes
- Low coolant level
- Radiator blockage
- Cooling fan failure on the 800AJ
What to do
Stop the JLG 800AJ and let engine cool; check coolant and clean radiator fins; if fan is not operating, service the fan drive.
Hydraulic System Fault
Common causes
- Low hydraulic oil
- Damaged hose on the 800AJ boom
- Clogged hydraulic filter
What to do
Park the 800AJ on level ground, check hydraulic fluid level with engine off, and inspect for leaks; replace filter if needed.
Platform Overload
Common causes
- Payload exceeds 800AJ rated capacity
- Uneven load distribution in platform
- Malfunctioning load sensor
What to do
Remove or redistribute load until alarm stops; verify with calibrated test weights; if persists, have load sensor recalibrated.
Engine Low Oil Pressure
Common causes
- Low engine oil level
- Oil pump failure
- Clogged oil filter on the 800AJ's diesel engine
What to do
Shut off engine immediately, check oil dipstick and add oil if low; if pressure remains low after startup, do not operate.
Battery Discharge
Common causes
- Alternator not charging on the 800AJ
- Loose battery cables
- Battery cell failure
What to do
Check battery connections and clean terminals; test alternator output; replace battery if it cannot hold charge.
Frequently Asked Questions
What does the red master warning light mean on my JLG 800AJ?
It indicates a critical fault, such as an engine shutdown or hydraulic failure, requiring immediate stop and troubleshooting.
How do I reset the overload warning on the JLG 800AJ?
Remove excess weight from the platform; the warning automatically clears when load returns to safe levels.
Why is the check engine light on after starting my 800AJ?
It usually indicates an engine sensor fault or emission issue; continue operation at reduced load and have it diagnosed soon.
Can I operate the JLG 800AJ with the master caution light on?
Yes, but you should identify and address the cause, such as low fuel or a maintenance reminder, to avoid a more serious issue.
What should I do if the hydraulic oil temperature light flashes on the 800AJ?
Reduce boom usage and allow the hydraulics to cool; check oil level and for any leaks; if persistent, service the hydraulic system.
How often should the air filter be changed on the JLG 800AJ?
Check it every 50 hours; replace when the restriction indicator shows red or after 250 hours in dusty conditions.