Saturn 4 Ultra 16K: the self-test fails (auto-leveling, mechanical sensor or resin tank not detected)

Symptom

In the pre-print self-test, the Saturn 4 Ultra 16K stops with «Auto-leveling failed, please troubleshoot», with a mechanical sensor error or with a resin tank error (when you try to print it says the tank is not detected).

Likely causes, from most to least likely

1. The printer stands on an unstable surface or near something that vibrates: other printers, fans, compressors or washing machines.
2. The build plate is not fitted or locked correctly, or its mounting screws are loose.
3. The cable of the mechanical leveling sensor or its adapter board is loose or damaged, or the spring (coiled) cable is tangled.
4. The resin tank is not a compatible one, is fitted the wrong way round, or its contact tips are deformed, covered by the film or dirty.
5. Poor connection between the adapter board and the tank contacts, or an open circuit in the tank.
6. The leveling sensor thresholds are off: Elegoo support checks this with a parameter file.

Checks to tell which one it is

• Note which error appears: auto-leveling, mechanical sensor or resin tank.
• Test with the printer on the floor or on a firm table, away from other machines.
• Check that the build plate is properly seated and locked.
• With the printer off, look at the tank contact tips: they must not be deformed, covered by the film or dirty.

Before you start

Uncured resin irritates skin and eyes: wear nitrile gloves and safety glasses, ventilate the room and do not look at the UV light. Before taking anything apart or cleaning it, switch the printer off and unplug it, unless a step says otherwise. If in any doubt, stop and ask a professional.

Step-by-step fix

1. Put the printer on a firm surface

   Place the printer on a stable, level surface, away from fans, compressors, washing machines or other printers. If in doubt, test it on the floor.

   Check: The self-test passes without error.

   If that does not fix it: Check the build plate (next step).

2. Check the build plate

   Wear nitrile gloves if there is resin around. Check that the build plate is correctly fitted and locked and tighten its mounting screws if they are loose.

   Check: The build plate is firm, with no play.

   If that does not fix it: Check the mechanical sensor (next step).

3. Check the mechanical sensor and its cable

   With the printer off, check that the cable between the mechanical sensor and the adapter board is firmly connected and undamaged. Also look at the spring cable: if it is tangled or twisted, rearrange it as shown in Elegoo's video for the Saturn 4 series. Replace the cable or the adapter board if damaged.

   Check: The self-test passes the mechanical sensor check.

   If that does not fix it: If the spring cable keeps causing trouble, replace it; if the error is about the tank, continue with the next step.

4. Check the resin tank

   Wear nitrile gloves and safety glasses and work with ventilation. Check that the tank is the original one for your model, fitted the right way round and with its screws tight. If the film covers the contact tips, pierce it just above them; if it is wrinkled or shifted, reposition or replace it. With the printer off, clean the contacts with a lint-free cloth and alcohol and let it evaporate before switching on.

   Check: The printer detects the tank in the self-test.

   If that does not fix it: Check the adapter board connections (next step).

5. Connections and continuity of the tank circuit

   With the printer off, check the adapter board wiring and reseat anything loose. If the contacts have oxidised areas, Elegoo says to sand them and apply conductive paste. With a multimeter in continuity mode, test the circuit of the tank contact tips and of the heating adapter board.

   Check: The multimeter beeps; if it shows «OL», that circuit is open.

   If that does not fix it: Replace the tank or the adapter board whose circuit is open.

6. Send the parameters to support (auto-leveling)

   If auto-leveling keeps failing, copy the Exporting.gcode file provided by Elegoo to the root of a USB drive, without renaming it or putting it in a folder, and print it: the printer will create the file 100MachineParams.gcode on the drive.

   Check: The file 100MachineParams.gcode appears on the USB drive.

   If that does not fix it: Send it to Elegoo support together with the type of resin you use and its viscosity.

Prevention

• Keep the printer on a firm surface away from vibrating appliances.
• Keep the tank contacts clean and dry and make sure the film does not cover them when you replace it.
• Use the original tank for your model.

Still not fixed?

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Printers it applies to

Elegoo Saturn 4 Ultra 16K.

Official sources

This guide summarises the official documentation linked here:

• Self Test: Auto-leveling failed · Elegoo
• Self Test: Mechanical Sensor Error · Elegoo
• Resin Tank Status Failure During Self-Test · Elegoo