How do I know when AdBlue tank is full MERCEDES-BENZ GLC Coupe (C253) (06.2016 - ...)

The Mercedes-Benz GLC does not usually show a direct "AdBlue tank full" indicator. Instead, the system issues low AdBlue warnings on the instrument cluster
These warnings may include:
"Top up AdBlue" or "Refill AdBlue": Appears when the AdBlue level drops to a certain value, indicating how many kilometers remain to drive before the system begins to limit engine power or prevent starting.
Messages about the number of kilometers remaining before the car cannot be started.
When you top up AdBlue, the system recognizes this and resets the warnings. If you fill the tank to the brim, the warnings will simply disappear and you will not see a message like "tank full", as this is not critical information for the driver, unlike a low level.

For your 2018 Mercedes-Benz GLC 300, here’s how to tell when the AdBlue tank is full and what indicators or warnings to watch for:

Indicators and Warning Lights
- Dashboard Warning Lights:
- A yellow AdBlue warning light appears when the AdBlue level is low, typically giving you around 1,500 to 1,650 miles remaining.
- A red warning light signals a critically low AdBlue level requiring immediate refill.
These lights are the primary indicators that your AdBlue tank needs topping up.
- AdBlue Level Display in Instrument Cluster:
Many Mercedes-Benz models, including the GLC, allow you to check the exact AdBlue level via the digital instrument cluster.
To check:
1. Press the Home button on the steering wheel controls.
2. Navigate to the Service menu.
3. Select the AdBlue option to view the remaining range or fluid level.
This shows how many miles you can still drive before needing to refill.

How to Know When the Tank Is Full
- When refilling, the AdBlue tank will only accept fluid until it reaches capacity (around 25 liters for the GLC).
- If you try to add more than the tank capacity, the filler will not accept additional fluid.
- After refilling, the warning light may remain on until the system resets, which can happen automatically after driving or may require a manual reset with a diagnostic tool if it persists.

Tips
- If the warning light stays on after refilling, don’t panic; it often clears after a short drive.
- If it does not clear, a manual reset using a Mercedes diagnostic tool (XENTRY or compatible OBD-II scanner) may be needed.
- Avoid letting the AdBlue level drop too low to prevent crystallization in the tank and sensor issues.

Summary
- Watch for yellow (low) and red (critical) AdBlue warning lights on your dashboard.
- Use the digital instrument cluster's Service menu to check the exact AdBlue level and remaining range.
- The tank holds about 25 liters; it will stop accepting fluid when full.
- After refilling, the warning light may take a short drive or a manual reset to clear.
- Regularly topping up prevents sensor issues and ensures smooth operation of your emission system.

This approach helps you monitor and maintain your AdBlue system effectively on your 2018 Mercedes GLC 300.