Never drive a pump straight from a pin. Use a switch and a separate supply.
What the message means
A pump draws far more current than a pin can give, and its coil produces voltage spikes when it switches off.
Fix it in this order
- Read the pump voltage and current rating.
- Switch it with a logic-level MOSFET, a transistor or a relay module.
- Put a flyback diode across the pump.
- Power the pump from a supply that fits its rating.
- Join the grounds of the pump supply and the board.
- Never run the pump dry, and keep wiring away from water.
Why it happens
A small pump motor draws far more current than a microcontroller pin can supply, and its start-up surge and switching spikes can reset the board.
Switch the pump through a relay or a logic-level MOSFET, power it from its own supply with a common ground, and put a flyback diode across the motor. Check the pump voltage and current in its specification.
If you see this, do this
| You see | Do this |
|---|---|
| Board resets when pump starts | Spike or shared supply. |
| Pump hums, no flow | Dry run or low voltage. |
Related
Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.