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Chapter 10 — Troubleshooting

Reference chapter — return here if something isn't working

Most problems in a Gaggiuino build fall into a small number of categories. Work through the relevant section methodically.

Nothing happens when I press the power switch

Check first: Is the machine plugged in?

If plugged in and switch pressed: - Does the switch latch? → If not, spring mod (Chapter 4) needs revisiting - Does anything light up (HMI, panel lamps)? → If not, check mains Socket L and Socket N connections (Chapter 5b Steps 1–2)

HMI screen is blank (machine is on)

  • Check the ribbon cable connections at both ends — PCB and screen
  • Check the PCB power: is the USB-C connected? (If using USB-C power for PCB only — not needed once installed in machine running from mains)
  • Verify the HMI connector on the PCB is fully seated

Wires melting or burning smell at the power switch

Unplug immediately

Melting wire insulation is a fire risk. Pull the mains plug from the wall before investigating.

This is almost always caused by a harness wire connected to the wrong switch terminal — specifically a permanently-live terminal rather than a switched one. A permanently-live terminal carries mains current regardless of switch state; the wire is not rated for continuous load at that position.

  1. Unplug the machine.
  2. Inspect the switch wiring. Identify which terminal each harness wire is on.
  3. Cross-reference against the official wiring diagram. Count pin positions from pin 1 with the switch oriented correctly.
  4. Move any incorrectly placed wire to the right terminal.
  5. Inspect the wire insulation on the affected wire for damage. If the insulation is cracked, bubbled, or charred, replace the entire wire — do not re-use damaged insulation.

Water leaking from top of boiler

This is almost always the thermocouple probe. The probe threads into the top of the boiler and must seal against the thread.

  1. Unplug the machine and let the boiler cool fully.
  2. Check that the thermocouple probe is hand-tight. It should be snug — not loose, not over-tightened.
  3. Verify that PTFE tape was applied to the probe thread (2–3 turns clockwise from the tip). PTFE tape is the primary seal here.
  4. If the probe was over-tightened and the boiler thread is damaged: the thread can sometimes be re-chased with an M4 tap. If damaged beyond repair, the boiler needs replacement.

Temperature reads incorrectly

Symptom Likely cause Fix
Stuck at room temp Thermocouple not heating boiler, or PCB not powering on Check power, check boiler heater SSR connections
Jumps wildly AC/DC cable interference Reroute signal cables away from AC wiring
Shows -200°C Open thermocouple circuit Reconnect thermocouple at PCB and probe ends
Shows 999°C Thermocouple polarity reversed or short Recheck thermocouple connector orientation
Reads 10°C above actual Normal — calibrate offset in Settings
Spikes above 100°C during shot Normal — Brew Delta feature, see Chapter 9 Step 3

Pressure reads 0 bar while pump is running

  • Check pressure sensor connector at PCB (must be fully seated and locked)
  • Verify sensor wire colour coding: VCC (typically red), GND (black), Signal (yellow or white)
  • Do NOT swap VCC and Signal — sensor will be destroyed

Machine switches off after 20 minutes

The Eco PCB bypass from Chapter 4 is not working. Recheck the C.1-to-C.2 bridge.

Pump makes noise but no water comes out

  • Check water tank is filled and seated properly
  • Check pump inlet hose is connected
  • Check PTB connections — the inline T-junction may have a leak pulling air
  • Check the 3-way valve (solenoid) wiring — 3WV L and 3WV N both need to be connected. If either is missing, the valve stays closed and water cannot reach the group head even while the pump runs.

Water flows but shot stops before reaching target weight

The profile has multiple stop conditions and a different one fired first.

  1. Pull a shot and watch the HMI — note which counter (time, weight, or waterPumped) stopped the shot.
  2. Go to Settings → Profiles → [profile name] → Edit and look at globalStopConditions.
  3. Increase or disable the stop condition that's triggering early.

Default profiles (e.g. IUIUIU Classic) use a waterPumped limit of 60mL as a safety stop — it fires before the weight goal if your grind is fine or puck resistance is high. This is expected behaviour, not a scales fault.

Pressure never exceeds 8 bar

OPV may be set too low. For EU machines set below 10 bar, and US machines (shipped at 9 bar): adjust OPV spring preload as described in Chapter 9, Step 5.

Scales read incorrectly

  • Verify load cell colour sequence: Red=E+, Black=E−, White=A+, Green=A−
  • Redo calibration (Settings → Scales → Calibration)
  • Check the Dual Scale Board PCB connector

Machine auto-shuts off after 20 minutes (E24)

The Eco PCB bypass from Chapter 4 is not working. The C.1–C.2 bridge is either missing or making poor contact.

  1. Unplug the machine.
  2. Remove the top panel and locate the monoblock connector.
  3. Find your C.1–C.2 bridge wire. Pull it gently — if it comes out, the crimp was bad. Re-crimp.
  4. If using Option B (splice): verify the Wago or butt splice is fully seated on both wires.
  5. If you are not sure which pins you bridged: recount from pin 1 on the housing face with a torch. Confirm both ends of your jumper are in C.1 and C.2 — not C.1 and C.3 or C.2 and C.4.

Wi-Fi won't connect

  1. On the HMI go to Settings → System → Wi-Fi and verify the SSID and password were entered correctly (passwords are case-sensitive).
  2. Gaggiuino connects to 2.4 GHz networks only — 5 GHz SSIDs will not appear in the scan list.
  3. If the correct SSID appears but connection fails: your router may be filtering by MAC address. Add the ESP32's MAC address to the allow list (the MAC is shown in Settings → System → About).
  4. If the SSID does not appear at all: move the machine closer to the router for initial setup. The ESP32 antenna is small.

OTA update failed / screen shows garbled output

The ESP32 can get into a bad state if power is lost during an OTA update.

  1. Power cycle the PCB (unplug USB-C, wait 10 seconds, reconnect).
  2. If the screen shows garbled output but the PCB still responds: go to Settings → System → Firmware Update and retry the OTA.
  3. If the screen does not boot at all after a failed OTA: you need to reflash the ESP32 via Path A (ST-Link). The STM32 core is unaffected — only the ESP32 UI firmware needs re-flashing.

Pump runs continuously and won't stop

Shut down immediately

A pump that runs without being commanded is either an SSR fault or a wiring short. Running the pump continuously overheats it and can cause pressure damage. Unplug the machine from the wall immediately.

  1. Unplug the machine.
  2. Check the SSR DC control terminals (the 3–32V side). Is there a wire shorting the two terminals together? That would keep the SSR permanently closed.
  3. Check the PCB SSR output connector — is it making unintended contact?
  4. If the wiring looks clean: the SSR itself may have failed in the closed position (a known failure mode of counterfeit or undersized SSRs). Replace the SSR.

Your SSR from the Peak Coffee kit is genuine and rated correctly. This failure is more common in self-sourced SSRs.

Screen shows "Releasing Pressure!" loop on boot, no brew function

This means the PCB detected an active brew switch signal at startup — either the switch wiring is connected to the wrong terminal, or the switch is stuck.

  1. Unplug the machine (safety first).
  2. Check the brew switch wiring: Switch L in (P5) and Switch L out (P4) must be on specific terminals. Verify against the official wiring diagram embedded in Stage 4 Installation.
  3. If the wiring looks correct: the brew switch may have a mechanical fault. Check that the switch is not stuck in the pressed position.
  4. The E24 brew switch has more terminals than older models — verify you are using the correct ones from the diagram, not the ones that look like the right position.

Brew button pressed — pump runs but no coffee comes out

  • Check the water tank is filled and properly seated.
  • Check the pump inlet hose (the hose from the tank to the pump) is connected and not kinked.
  • Check the PTB connections — a small air leak in the T-junction can prevent the pump from building pressure.
  • Run a flush cycle (Flush button on the HMI) for 5 seconds to prime the system after any water path work.

Pressure reads correctly but shot flow seems wrong

  • Gaggiuino controls the pump via a dimmer — if the pump group wiring (Pump L / Pump N) is connected to the wrong terminals, the dimmer has no effect.
  • Verify Pump L (with the inline fuse) is on the Live side of the pump, not the Neutral side.
  • Check that the pump fuse has not blown (inline fuse in the Pump L wire — swap it for a known-good fuse of the same rating).

Still stuck?

  1. Search the Gaggiuino Discord — most problems have appeared before and are documented in search results
  2. Post in Discord with: a photo of your wiring, your machine model, your firmware version, and a clear description of the symptom and what you have already tried
  3. Check the official Gaggiuino documentation for error code reference and advanced calibration

The community is active and genuinely helpful. A clear question with a wiring photo gets an answer quickly.