Grindmaster Grind’n Brew Error Code Er1: Water Fill Error
Er1 is a water fill error: the water-full detection failed and the fill valve has been on for at least 5 minutes. Check that the water supply is on. To clear it, hold the UP key for 5 seconds, reset power to the unit, or enter field test mode.
High: water fill and heat shut off and brewing is disabled until the error is cleared.
- Code
- Er1
- Maker
- Grindmaster
- Equipment
- Coffee brewers
- Applies to
- Grind'n Brew GNB-10H/11H/20H/21H
What does Grindmaster error code Er1 mean?
The brewer fills its tank through a fill valve and watches for a water-full signal to stop. If the signal never arrives and the valve has been on for at least 5 minutes, the control gives up and shows Er1, a water fill error. The manual's troubleshooting guide lists a water supply turned off, a fill valve that stays on too long and a defective fill valve, and says to replace the valve if it is defective. With any of the water system errors, water fill and heat shut off and brewing is disabled, while grinding is still allowed. The display shows the error when the unit is idle and the Basket Out light flashes. To clear the error, the manual gives three ways: hold the UP key for 5 seconds, reset power to the unit, or enter field test mode. Clearing does not remove the cause. If the supply is off, the control will reach the same limit again. If the water-full detection is failing, the fill will run long every time.
Affected models and control systems
Grindmaster Grind'n Brew GNB-10H, GNB-11H, GNB-20H and GNB-21H.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Er1 on the display when the unit is idle
- Basket Out light flashing
- Brewing disabled
- Grinding still works
Possible causes
Listed in Grindmaster's documentation
- Water fill valve on too long
- Water supply turned off
Other likely causes — what usually sits behind error code Er1 on this control. A technician confirms which one it is before any part is replaced.
- Water-full detection input not reading because of scale or a dirty probe
- Supply pressure too low to reach the full signal in time
- Fill valve held open by debris
Safe checks before calling for service
- Check that the water supply valve to the brewer is open and the inlet line is not kinked.
- Hold the UP key for 5 seconds, or switch the power off and on.
- Try one brew.
- If Er1 returns, note whether water was filling or not, then call us.
How a technician diagnoses error code Er1
- Read the display and confirm Er1.
- Check the water supply and inlet strainer.
- Check the fill valve operation.
- Check the water-full detection input.
- Replace the fill valve if it is defective.
- The fill valve and detection circuit carry line voltage.
- Field test mode is a service function.
- Telling a bad valve from a failed detector needs a meter.
How error code Er1 differs from similar codes
Er1 is the water fill error; Er2 and Er3 are thermistor errors and Er4 is the heater error.
Technical reference
- Maker documentation
- Grindmaster owner support
- Edition
- Form # BW-354-03, 0516 (copyright 2016)
- Models / control
- Grind'n Brew GNB-10H/11H/20H/21H
- Section
- Programming section 'Water System Errors' (printed p.10) and Troubleshooting Guide (printed p.14)
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Grindmaster coffee brewer error codes
How do I clear Er1?
Hold the UP key for 5 seconds, reset power, or enter field test mode.
Why did it take 5 minutes?
The manual says Er1 is set when the fill valve has been on for at least 5 minutes.
Can it still grind?
Yes. Grinding is still allowed.
Need help with Grindmaster error code Er1?
A technician confirms the cause on site and gives you the price in writing before any work starts.