Repairing appliances is a passion of mine. It’s rewarding, saves money, and more importantly, helps me design more reliable products. Tools, appliances, and tech often fail in predictable ways – and they’re usually cheap and easy to fix if you know how.
In this case, an expensive Makita vacuum cleaner was practically given away because the self-cleaning filter function had failed. The cause? A single loose screw.
This guide applies to the Makita VC4210M, VC4210L, VC4210MX1, VC4210MX2, and Nilfisk ATTIX 33 / ATTIX 44 models – all of which share the same automatic self-cleaning filter system (also known as InfiniClean). If your vacuum no longer makes the loud “thumping” sound during use, this post should help you diagnose and repair it.
Understanding the Self-Cleaning System
The self-cleaning feature uses a valve located above the flat panel filter, between the motor impeller and the dust collection chamber. This valve is driven by a 24V solenoid that rapidly opens and closes to reverse airflow and clean the filter.
In my repair, the screw that connected the valve to the solenoid had come loose. The solenoid was energising, but the plunger wasn’t moving – meaning the cleaning valve never operated. Before You Start
- Check the power switch position. The 3 o’clock and 9 o’clock switch positions disable the auto-clean function. Use the 2 o’clock or 11 o’clock positions to enable it.
- Confirm that filters are clean. While dirty filters can reduce cleaning efficiency, in this case the loose screw was the true cause – not the filters.
- Try the manual test. Cover the hose inlet with your hand while running the vacuum. Supposedly, this should trigger a strong cleaning pulse. If it doesn’t, mechanical or electrical faults are likely.
Step-by-Step Repair
First, remove the upper cover of the filter door to expose the valve and solenoid. With this cover off, I could see the solenoid twitch very slightly when current was applied; however, the valve did not move. With this cover off, you can press the valve opposite to the solenoid and check that the valve is moving freely.
Remove the second cover to fully expose the solenoid. Remove the solenoid clamp.
The valve body (left arrow) moves independently of the solenoid plunger (right arrow). These should be connected, but the screw connecting them has come loose.
Remove the valve cover and extract the valve and solenoid. The loose screw is rattling inside the valve.
The end cap on the valve is a press-fit and comes loose by hand. The offending screw falls out freely.
Reinstalling the screw inside the valve to reconnect it to the solenoid plunger requires a long, narrow Torx screwdriver. Loctite retaining compound will be crucial to keeping the valve working. I used blue Loctite 243 threadlocker - as this is all I have on hand - but a more aggressive retaining compound would probably be more suitable.
With that installed, the reassembly process is straight-forward - simply put it all back together the same way as it came apart. This fix immediately solved the issue and has been faultless since.
Design Thoughts
From a design perspective, this is a weak point. The system relies on a single screw under repeated impact loads, with only threadlocker keeping it secure. It’s no surprise this connection eventually fails.
Aside from that, the rest of the construction is excellent. The plastic mouldings, seals, and screw bosses are robust and well-designed. All fasteners are self-tapping Torx screws of the same size, and no security Torx or fragile snap-fits are used – making disassembly easy.
The replacement part is listed online for over $300 and includes the entire solenoid valve assembly. In fact, installing the replacement part would take more time than repairing this screw because you have to disassemble the main body to wire the new solenoid into the control PCB.
Next, I will be disassembling the main body to rewire this disastrous repair the previous owner left me with 😵
