HMS 0300-C300-0001-0002: filter switch flap current sensor malfunction
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HMS 0300-C300-0001-0002 means the current sensor on the filter switch flap has malfunctioned, from an open circuit or a hardware fault. Without that reading the printer has no way to confirm the flap actually moved, so it stops commanding it. The flap then sits wherever it was, and your filtration is whatever that position happens to give you.
Affected machines: H2 and P2S. Of the flap codes this is the one with an air-quality consequence, because the filter path is what removes what ABS and ASA give off. Knowing which position the flap is stuck in matters more here than on the chamber flap.
Where to buy
Find out where the flap is stuck
Before diagnosing anything, look at the flap and note its position. If it is stuck with the filter engaged, you have lost nothing but flexibility: PLA will run slightly warmer than ideal and everything else is fine. If it is stuck in bypass, then ABS and ASA are out of the question until it is fixed or you have external extraction.
Then check the mechanism by hand with the machine off. A flap that binds makes the drive draw an odd current, and while that is not this fault exactly, it is worth eliminating before you start suspecting the board.
Then the loom. An open circuit is one of the two named causes, so reseat both ends and inspect the run for chafing where it passes the moving assembly. If the flap is free and the loom is intact, the sensing hardware is what remains, and that is a service item rather than a part.
Printer reports the filter switch flap current sensor is malfunctioning
Open circuit in the flap drive loom, a binding flap, or a failed sensing circuit
- Power off at the wall and let the chamber cool.
- Note which position the flap is stuck in, because that decides what you can safely print meanwhile.
- Move the flap by hand through its travel, checking for binding and cleaning dust from the housing.
- Reseat the flap actuator connector at both ends and inspect the loom for a chafed section.
- Replace the filter if it is old, since a swollen filter can foul the flap and distort the drive current.
- If the flap is free and the wiring is sound, record the code and raise a support ticket.
Print PLA and PETG in the meantime, and keep ABS and ASA for after the repair unless you have proper extraction. That is a decision about the air in your room rather than about the printer, which is why it is worth stating plainly.
The mechanical fault on the same flap is filter switch flap malfunction, and the position sensor version is the flap Hall sensor fault. Our page on extraction and filtration explains what is at stake, and the troubleshooting index covers the rest.
HMS 0300-C300-0001-0002 FAQ
Can I print ABS with this fault?
Only if the flap is stuck with the filter engaged, or you have external extraction. Otherwise no.
Is there a part I can buy?
Not for the flap drive. The filter and the auxiliary fan on the same path are the parts that exist.
Why does the printer stop using the flap?
Because without current feedback it cannot confirm the flap moved, and it will not assume.
Could an old filter cause this?
It can contribute. A swollen filter fouls the flap and changes the drive current, so change it while you are in there.
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