Heater not reaching temperature
The extruder or bed heater fails to reach the target temperature, drops unexpectedly during printing, or overshoots and oscillates.
Symptoms
Section titled “Symptoms”- Klipper error: “Heater extruder not heating at expected rate” — print aborted
- Temperature drops 20–30°C suddenly during a print (especially in the Nozzle Zone, T2)
- Temperature overshoots by 10–15°C before stabilizing (especially the Feeding Zone, T0)
- Temperature oscillates instead of holding steady
- Bed heater error at startup (see Bed heater on wrong outlet)
- Klipper reads a temperature that cannot be real — deeply negative, often flickering, around -90 °C → sensor fault (see Temperature sensor disconnected)
Zone behavior to know first
Section titled “Zone behavior to know first”The G1 has three independent heating zones (Multi-Heating Zones):
| Zone | Klipper name | Location | Typical behavior |
|---|---|---|---|
| Feeding Zone | extruder (T0) | Top of barrel | Can overshoot its setpoint by 10–15°C at first |
| Melting Zone | extruder1 (T1) | Middle | Stable |
| Nozzle Zone | extruder2 (T2) | Bottom, near nozzle | Closest to cooling fan — most vulnerable to temperature drops |
Cause 1 — Cooling fans too strong
Section titled “Cause 1 — Cooling fans too strong”Symptom
Section titled “Symptom”The Nozzle Zone (T2) temperature drops during printing when the part-cooling fans run hard.
Why it happens
Section titled “Why it happens”Part-cooling fans run too strong pull the Nozzle Zone (T2) temperature down, and Klipper shuts down with a heating error.
Cause 2 — It is not the PID
Section titled “Cause 2 — It is not the PID”Symptom
Section titled “Symptom”Temperature oscillates or overshoots, and the instinct is to re-tune.
Cause 3 — Temperature sensor loose or failing
Section titled “Cause 3 — Temperature sensor loose or failing”Symptom
Section titled “Symptom”Temperature reading is erratic, jumps suddenly, or goes impossibly negative — an open circuit lands around -90 °C, flickering. Often appears mid-print.
- Check the JST immediately after the sensor first, then the JST on the Octopus, then the ethernet cable carrying the signal
- Test by bringing the zone to temperature and gently moving each connector while watching the graph: the reading must stay stable
- If contact is intermittent, removing the JST by wiring the sensor through to the breakout board is a valid field fix, because it takes the connector out of the signal path
- The permanent fix is the update kit: three sensors in the metal cartridge plus the calibration values for
printer.cfg
Full detail: Temperature sensor disconnected and the current sensor.
Cause 4 — Feeding Zone (T0) temperature too high
Section titled “Cause 4 — Feeding Zone (T0) temperature too high”Symptom
Section titled “Symptom”Pellets melting inside the hopper neck — visible as material fusing at the top of the barrel. Motor may click.
Reduce the Feeding Zone (T0) temperature by 10–15°C. It tends to run hotter than the setpoint at first. If it overshoots, reduce the target until it stabilizes.
Cause 5 — Power supply voltage drop (vacuum causes dip)
Section titled “Cause 5 — Power supply voltage drop (vacuum causes dip)”Symptom
Section titled “Symptom”Random temperature drops or MCU errors at the moment the vacuum pump starts or stops.
Why it happens
Section titled “Why it happens”The vacuum is a ~1 kW load whose motor draws several times that at startup. With everything heating, the printer alone is already near 3 kW — about 13 A — so on a single 16 A circuit the inrush is what pushes the voltage down far enough to disturb heater control and trip Klipper’s safety checks.
- Split the load across the two mains inputs on the power box — one circuit for printer and vacuum, one for the bed. This addresses the cause rather than moving it
- Never share a power strip or extension reel between printer and vacuum
Full breakdown, with the load table: Case A in Hopper suction problems.
Cause 6 — Bed heater error at startup
Section titled “Cause 6 — Bed heater error at startup”If the bed is the heater not reaching temperature, and the error appears immediately at startup, the bed heater cable is likely in the wrong outlet. See Bed heater on wrong outlet.
If instead the bed simply never warms up, with no error at all, the usual cause is that the bed SSR is not being told to switch: two of the four screws on connector [2] of the power box board are the SSR BED signal, and one that has not bitten leaves the socket dead. See the two power box connectors.
And if the bed reads -99 °C or flickers, check its sensor connector — the bed has two sensors and only one is plugged in, see The bed has two temperature sensors.
After fixing
Section titled “After fixing”- Run a temperature stability test: heat to print temperature and watch the graph for 5 minutes
- If temperatures are stable → run a short test print (single layer skirt)
- If temperatures still drop → contact Ginger Additive support with
klippy.log(downloadable from Machine section in G1OS dashboard)