Automatic faucet stopped working

What this error means

The documented causes, in order: dead or low batteries (Sloan's low-battery signature is an intermittently flashing red LED; Moen specifies checking installation and using alkalines), a dirty or obstructed sensor lens (including protective stickers never removed after install — genuinely documented), and the same clogged aerator that afflicts manual faucets. No water at all with good batteries points to the solenoid valve.

Symptoms

• No response to hands
• Intermittent red LED (battery warning)
• Weak dribble (aerator, not sensor)

Try this first (safe DIY steps)

1. Replace the batteries first (under-sink control box or spout base; alkaline only)
2. Wipe the sensor lens clean; check for leftover protective film
3. Clean the aerator (see the aerator guide)
4. Check the under-sink supply stops are fully open
5. Still dead: the solenoid — part is replaceable on commercial models

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

Solenoid replacement or hardwired/transformer models beyond battery-and-lens basics — plumber or the manufacturer's parts line.