HMS 1A00-3300-0001-0040: Rack Position Detection Sensor Is Open-Circuit
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HMS 1A00-3300-0001-0040 means the sensor that reports where the hotend rack is has gone open-circuit, and Bambu asks you to reconnect the sensor cable or replace the sensor. This is the rack’s own position sensor, not the hotend presence sensor, so it is a different cable in a different place.
The code group tells you which: 3000 is the toolhead, 3300 is the rack. That saves opening the wrong side.
Where to buy
Reseat the rack sensor connector
Power down and find the connector at the rack end rather than at the toolhead. It moves less than the toolhead cable but it gets disturbed whenever the rack is removed or refitted, which is exactly when this fault tends to appear. Reseat it until it clicks and retry.
Then follow the run
Look for a pinch point where the cable passes the frame, and for a conductor broken inside insulation that still looks perfect. An open circuit with no visible damage is almost always one of those two.
What stops working without it
Position reporting is what homing and calibration both rely on, so expect those to fail alongside it. If you are seeing HMS 1A00-1100-0002-0002 as well, treat this sensor as the single cause rather than chasing a homing fault separately.
How HMS 1A00-3300-0001-0040 differs from the toolhead sensor
The toolhead presence sensor is HMS 1A00-3000-0001-0040. That one answers whether a hotend is held; this one answers where the rack is. They fail independently and cost different parts, which is why the code prefix matters more than the last digits.
Confirm before you buy
A continuity check across the circuit separates a broken cable from a dead sensor, and that decides the order. What this class of sensing does elsewhere on a printer is covered in bed levelling sensors.
HMS 1A00-3300-0001-0040 FAQ
Can I print with it open?
Single-tool, usually. Swapping and rack calibration are out.
Did refitting the rack cause it?
Very likely. That is when this connector gets disturbed.
Is there a short-circuit version?
Yes, and it reads differently — check the last digit of the code before ordering.
Will setup clear it?
No. Setup needs the sensor working, not the other way round — see HMS 1A00-1200-0002-0010.
The same rack sensor fails the other way too. HMS 1A00-3300-0001-0041 is the short-circuit version, where pinched insulation and a bent pin come before a loose connector.
LayerWalker
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