Bed heater on wrong outlet

The bed heater plugged into the wrong socket on the power box — typically the always-on forced one — so it heats by itself even when the firmware doesn’t command it. Almost always a first-boot mistake, but easy to fix.

Symptoms

• The bed heats up on its own even in standby, with no user command
• Bed temperature rises uncontrollably above the target
• The printer shuts down reporting the bed over its 110°C limit
• You never asked for bed heat, and the bed is hot

Why this happens

The G1 has three power sockets on the power box (under the panel box, right side), each with a different role and each labelled — read the label rather than counting positions (see Power outlets (power box)):

Socket label	Function
Forced	Free / always-on — never use for the bed
Feeding	Vacuum pump
Bed	Bed heater — this is where it goes

Two of the three sockets are switched by a relay. The Bed socket’s relay is driven by the bed’s watermark controller — that is what turns the heater on and off around the target. The Feeding socket’s relay is driven by the capacitive level sensor.

The Forced socket has no relay. It is permanently live, meant for a laptop charger or a third-party camera, and nothing the firmware does will switch it.

Diagnosis

Look at the power box — under the panel box, on the right side — and trace where the bed heater’s power cable is plugged in. The sockets are labelled. If you are asking support about this, send a photo of the box with the wiring visible.

Fix

A Klipper shutdown will not save you here

When Klipper shuts down — including on the bed’s own 110°C max_temp — the Bed and Feeding relays drop and those sockets go dead. The Forced socket does not: it has no relay to drop.

So a bed on the Forced socket keeps heating after the printer has stopped, with nothing regulating it. Switch the machine off at the mains, not just at the front switch, then move the plug.

1. Switch the machine off at the mains
2. Unplug the bed heater cable from the wrong socket
3. Plug it into the socket labelled bed
4. Power the printer back on
5. Verify that the bed stays cold until you command a heat-up

How to prevent

• Check the power box socket labels at first boot — each socket is marked (feeding / bed / forced)
• Run through the Electrical connections and first boot checklist before powering on a new machine
• Frequent occurrence right after first assembly or after moving the machine to a new location

Notes

• One of the most common first-boot wiring mistakes
• Check this before suspecting a thermistor or a firmware bug

Related notes

• Power outlets (power box)
• Bed heater
• Electrical connections and first boot