AMS 2 Pro or AMS HT: the printer doesn't detect it or it won't dry the filament

Symptom

The printer does not recognise the AMS 2 Pro or the AMS HT: on the AMS 2 Pro, the LEDs of all four slots double-flash red and it does not appear on the screen or in the software. Or the drying function will not start or dries poorly.

Likely causes, from most to least likely

1. Wrong 6-pin cable: the first-generation AMS cable (1.1 mm step) or a third-party one does not communicate reliably with the AMS 2 Pro or AMS HT, which use the new cable (2.5 mm step).
2. 6-pin connector not fully seated or with a bent pin, or the internal bus cable loose inside the AMS.
3. No power for drying: with an X1, P1 or A1, each AMS 2 Pro needs its own power adapter to dry, and the AMS HT always dries using its own mains cable.
4. Several AMS 2 Pro units drying on a P2S or H2 series printer: the printer powers drying for only one, the others need adapters.
5. Trying to dry without a connection: the AMS 2 Pro and AMS HT cannot dry on their own; they must be connected by the 6-pin cable to a powered-on printer.
6. While the printer is printing or loading filament, drying power drops so printing gets priority.

Checks to tell which one it is

• Look at the step on the cable connector: the new one supplied with the AMS 2 Pro and AMS HT is higher (2.5 mm) than the old AMS one (1.1 mm).
• If you have a first-generation AMS, connect it instead: if it works, the AMS 2 Pro is at fault; if not, the printer or buffer is.
• Check which printer you use it with, how many AMS units dry at once and whether each one has its power supply.
• On the AMS HT, if you print TPU through the TPU port at the rear of the lid, it cannot dry while feeding through that port.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Use the right cable and reseat it

   Switch the printer off. Connect the AMS 2 Pro or AMS HT with the new 6-pin cable from its box (the old AMS works with it too) and do not use third-party cables. Unplug and replug the cable and check that no pin is bent.

   Check: At power-on, the AMS appears on the screen and in Bambu Studio and the LEDs stop flashing red.

   If that does not fix it: Do a cross-check with another AMS (next step).

2. Cross-check

   If you have another working AMS, connect it in its place with the same cable and power on.

   Check: You know whether the AMS 2 Pro or the printer and buffer are at fault.

   If that does not fix it: If the AMS 2 Pro is the faulty one, check its internal cable (next step).

3. Check the internal bus cable

   With the printer off and following the Bambu Lab disassembly guide, open the AMS 2 Pro and check whether the internal bus signal cable has come loose; unlock the connector latch, reseat it and reassemble.

   Check: At power-on, the printer detects the AMS.

   If that does not fix it: Contact Bambu Lab support; the multimeter measurements in its guide are only for people who already own one and know how to use it.

4. Power the drying function

   With an X1, P1 or A1, connect every AMS 2 Pro that will dry to its official adapter (24 V, 4 A). With a P2S or H2 series printer, one unit can dry from the printer's power and drying more at once needs adapters. The AMS HT always dries on its own mains cable. Do not use third-party adapters.

   Check: Drying starts from the screen or from the device tab in Bambu Studio.

   If that does not fix it: Check the 6-pin connection and the firmware (next step).

5. Dry while connected and with current firmware

   Keep the AMS connected by the 6-pin cable to a powered-on printer: there is no offline drying. To dry while printing, update the firmware (H2D from 01.03.00.00; H2S and P2S from 01.02.00.00) and start drying from the device tab in Bambu Studio. On a P2S without an adapter, while it powers drying it cannot heat or move the axes.

   Check: Drying works and, if your printer supports it, continues during the print.

   If that does not fix it: If drying will not start with everything connected correctly, contact Bambu Lab support.

Prevention

• Keep the old AMS cables separate so they do not get mixed up with the new ones.
• Use official accessories only: a third-party adapter can damage the AMS and affect the warranty.
• With TPU on the AMS HT, use its TPU port and treat the AMS as a dry box: it does not auto-load TPU.

Still not fixed?

Tell usi3d's AI about your case: choose your printer, describe what you see and add photos if you like. It proposes checks step by step, with their sources.

Tell the AI about your case

Printers it applies to

Bambu Lab's FDM printers: A1, A1 mini, A2L, H2C, H2D, H2D Pro, H2S, P1P, P1S, P2S, X1, X1 Carbon, X1E and X2D.

Official sources

This guide summarises the official documentation linked here:

• AMS 2 Pro is not detected by the printer · Bambu Lab
• AMS 2 Pro and AMS HT - Frequently Asked Questions · Bambu Lab
• Connection Guide for Multiple AMS Units with Different Printer Models · Bambu Lab