The John Deere 3520 compact utility tractor features a range of warning indicators to keep you informed of engine, transmission, and hydraulic system status. Understanding these lights helps prevent costly downtime and ensures safe operation in the field.
John Deere 3520 Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Master Warning (Stop) | RED | A critical issue detected in the engine, transmission, or hydraulics—do not continue operation. | Immediately stop the engine and consult the operator's manual for troubleshooting. | |
| Master Caution | AMBER | A non-critical fault exists that may require attention soon. | Check the LCD display for specific warnings and schedule service as needed. | |
| Check Engine (MIL) | AMBER | Emission control or engine performance issue detected by the ECU. | Have the engine diagnosed with the JD Service Advisor tool. | |
| Engine Oil Pressure | RED | Oil pressure below safe level—engine damage can occur quickly. | Stop engine, check oil level and filter; if ok, call dealer. | |
| Battery / Charging | RED | Charging system voltage too high or low. | Check alternator belt, connections; test battery charge. | |
| Coolant Temperature | RED | Engine coolant temperature has exceeded safe limit. | Immediately idle engine, check coolant level and fan belt. | |
| Transmission Temp | AMBER | Hydrostatic or gear transmission oil temperature is elevated. | Reduce load and shift to lower gear; allow cooling. | |
| Parking Brake | RED | Parking brake is engaged while trying to drive. | Release parking brake before moving the tractor. | |
| Glow Plug / Preheat | AMBER | Glow plugs are activated during cold start; wait for indicator to turn off. | Turn key to preheat position until light goes out, then start. | |
| Low Fuel | AMBER | Fuel level is low; you have limited range before shutdown. | Refuel with diesel as soon as possible. | |
| High Beam | BLUE | High beam headlights are turned on. | Dim when approaching other vehicles. | |
| Hydraulic System | RED | Hydraulic system pressure or temperature fault detected. | Stop tractor, check hydraulic oil level and filter. | |
| Fasten Seat Belt | RED | Seat belt is not fastened while operator is seated. | Fasten seat belt before operating. | |
| PTO Engaged | GREEN | Rear PTO is engaged and rotating. | Disengage PTO before leaving seat or working around shaft. | |
| Differential Lock | AMBER | Axle differential lock is engaged for extra traction. | Release diff lock before turning on hard surfaces. | |
| Work Lights | GREEN | Rear or front work lights are switched on. | Turn off when not needed to conserve battery. | |
| Service / Hour Meter | AMBER | Scheduled maintenance interval has been reached. | Perform required service per operator's manual (e.g., oil change, filter). |
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
- Faulty thermostat
- Clogged radiator fins
What to do
Allow engine to cool, check coolant level in overflow tank, clean radiator screen; if recurring, inspect water pump and thermostat.
Low Engine Oil Pressure
Common causes
- Low oil level
- Worn oil pump
- Clogged oil filter
What to do
Engine off, check dipstick; top up with 15W-40 diesel oil; replace filter if due; persistent issue may require dealer inspection.
Battery Not Charging
Common causes
- Loose alternator belt
- Faulty alternator
- Corroded battery terminals
What to do
Check belt tension and condition; clean terminals; test alternator output (should be ~14V). Replace alternator if defective.
Transmission Overheating
Common causes
- Overloading
- Low transmission fluid
- Clogged cooler
What to do
Reduce load, shift to lower range; check fluid level at dipstick (tractor level); clean external cooler fins.
Frequently Asked Questions
The check engine light stays on after starting my 3520. What should I do?
If the light remains on, there is an active fault. The tractor will still run, but performance may be reduced. Use the diagnostic menu on the LCD to read the code, then contact your dealer with the code.
Why does my glow plug light blink?
A blinking glow plug indicator on the 3520 means the system is cycling after start to reduce white smoke. If it stays on or blinks rapidly, there may be a glow plug module fault.
What does the red Master Warning light mean?
The Master Warning (stop) illuminates when a critical fault is detected in engine, transmission, or hydraulics. You must stop the engine immediately and consult the manual or dealer.
How do I reset the service interval light on my 3520?
Turn key to ON, press the 'Menu' button, navigate to 'Maintenance', and select 'Reset Service Interval'. Confirm. This only works after the required service is completed.
The transmission temperature light came on while baling. What now?
Reduce engine speed and shift to a lower gear to decrease load. Park in the shade and let the transmission cool with the engine idling. Check fluid level when cool.
My battery light stays on dimly. Is that normal?
No, it indicates a charging problem. Check the alternator belt tension and battery connections. If the belt is fine, the alternator may be failing.