It's usually the battery. Your symptoms do sound like battery. I've picked up a few for free, replaced the battery, and they work perfectly. Non branded batteries are a bit hit and miss but the last couple have been fine. Your symptoms do sound like battery. Easy to change, just two screws, one is a bit hidden.

Does the long extension have powered spinning brushes? Of so, are they spinning? They can get clogged and perhaps create resistance?

Or something.

@cb When you get to the bottom of it, please let us know. Ours is doing (sounds like) a very similar thing. Runs for a few mins, and then starts 'pulsing' on and off. When I empty the canister of dust, its fine for a few mins more, then does it again. But I'm reasonably confident it's not the battery, as that was new about a year ago, and a Dyson original rather than a knock-off other brand. It's weird, and irritating.

But I'm reasonably confident it's not the battery, as that was new about a year ago, and a Dyson original 

Is it definitely an original? There are fakes out there. Those are exactly the symptoms of a dying battety

Thanks all, why would the unit run perfectly well with the short tool on and not with the longer version.  If the battery were dying, would it also happen when the short tool is on?  Maybe last longer before pulsing but it would happen surely?

Yeah, pretty sure we went direct to Dyson.. I think so, anyway

Likely battery. My recommendation would be to look at the battery convertors to power tool batteries, as they seem to work a lot better. 

Ours did this, something is block the air path some where, did you properly clean the filters?

Ours did this and it was the long cylindrical filter which caused it. 
Remove the filter and wash it under running water then refit it once dry. 
It cured the pulsing on ours. 

Posted by: cb

↑

Thanks all, why would the unit run perfectly well with the short tool on and not with the longer version.  If the battery were dying, would it also happen when the short tool is on?  Maybe last longer before pulsing but it would happen surely?

They have monitoring in the battery that shuts it down when certain limits are met. This is normal in all LIon batteries but as far as can tell it is super sensitive in Dysons. Far more than any other tool I've owned. 

If you go for an aftermarket replacement it's only £25 or so to find out. If it turns out to be something else you end up with a spare for when the battery does inevitably fail.

solve my Dyson Issue

Buy a vacuum from someone who isn't a brexiteer?

solve my Dyson Issue

Buy a vacuum from someone who isn't a brexiteer?

We had this issue with the Dyson at work. 

It was resolved by removing all the filters and battery, checking for blockages then throwing the whole lot in the bin and buying a Shark.

Dysons are absolute garbage. Over priced, poor quality plastic tat. 

Buy a Vax. More reliable than a Dyson and a Shark - the shark just died, and this was a mains one. Dysons fall to bits.

Thanks all (most), I guess I'll have to try a battery!  We have Samsungs at work and they do seem much better but the Dyson remains (unlike him) until it dies...

We have the same problem. I would agree the Shark is significantly better than the Dyson. I found any weight (as an attachment) pulled the battery connection apart causing it to cut out. Nothing to do with the battery itself.  I’ve mostly fixed it by Velcro strapping the cyclinder to the handle to pull it tight. It’s a pain in the arse. 

Been down this road with ours. I initially assumed the battery was goosed so bought another, which also pulsed. Had a deeper dive on the official Dyson website. Pulsing = Blockage / flow restriction somewhere. I had previously checked the filters and nozzle before buying the battery so was confident it wasn't that. Rechecked the machine, including probing a finger into a hidden part of the ducting, only to find a neatly jammed chunky wooden offcut sooked up from a DIY job about 18 months earlier.... just about the time it started pulsing. Removed blockage and hey presto, I now have a fully functioning Dyson with 2 batteries. Note to self; RTFM before shelling out on batteries.

My parent's one does this and I think when I looked into it you have to take it apart and clean internal stuff. It had previously died so I replaced the battery & motor unit (from some 3rd party place rather than Dyson 🙁 ), ran fine for a couple of months and now pulses and complains about blocked airway but I've thoroughly cleaned that (and ensured no other blockages) but it still does it - however it does it even without any tool plugged in so doesn't sound quite the same as yours. 

Ours does the exact same thing. There seems to be a pattern emerging.

I long ago concluded it's just not very good and won't buy them again.

Ours is about 10 years old now and had a good few repairs and it has never been battery when it starts pulsing. Normally related to a blockage or the filter. I replace the filters with aftermarket cheapo ones from ebay or amazon from time to time. 

Mine is def not the filters, replaced the long removable one with a brand new one, cleaned the filter units in the main housing and still no joy.  I can see fresh air everywhere a blockage might be so battery is my only remaining option!  The filters can cause similar problems, which is why I stripped everything to begin with.

Mine does this. A good clean out with an air compressor works, which makes me suspect gunk in the system. I hope the bloody thing dies soon so we can buy something less shit.

I solved my Dyson issue by replacing it with a Miele, which has been faultless for over ten years.

Just be aware that most aftermarket batteries for laptops and Dysons don't have the battery balance circuit and wiring in them IME.

So they start off great but performance falls away by the time most of the reviews have been written. 

Still, the remaining good cells from old Dyson batteries get soldered in parallel into my work radio, it runs for days now from one charge and is heavy enough to stay put 🙂

Defintely the battery. I had this on mine, it was fine with the small attachment but with the long pole and sweeper head it died after a few seconds. I think the brush bar is powered so the draw from that was enough for it to die. New aftermarket battery solved the issue and it has worked happily for 3 years

Buy a vac from a company that isn't activley trying to rip of the UK economy.

I would say Dyson sucks, but it really doesn't... it's just over priced 'tat' from an offshore company that pays no tax.

Check the entire airflow path from one end to the other thoroughly. 

if it is really clean then try a new, previously unused filter. 

if that doesn’t resolve things then get a new battery. 

from an offshore company that pays no tax.

They have a huge UK presence and subsequent tax bill and James Dyson was the 6th largest UK tax payer last year. While personally I'd like to see to rich taxed more and loopholes closed, within the system we have this isn't really a stick to beat Dyson with.

As i read through I remembered this happened to ours not all that long ago... and guess what, the Dyson website tells you what to do. I did and it worked.

My Dyson cordless vacuum cleaner is pulsing/switching on and off/has a blockage light. What does this mean? | Dyson Community

Mystery continues.  New battery arrived, seemed to have done the trick but now pulsing again!  There are only two places where blockages could be and I can see daylight through both (the long stick extension and the cleaning head).  No idea what to do now!

All right, I realise I've bored everyone now and I'm just talking to myself..

I prefer to hear the end of these types of thread so just updating.  After the new battery failed to solve the issue, I stripped the cleaning head again, found a chunk more muck at the base of the cleaning brush and assumed that I'd nailed it.  Nope!

More digging and it seems as though there are two wire connectors in the cleaning head.  These are the problem!  They look very second hand at first view.  Will strip right down tomorrow and see if I can fix these, otherwise its just a short version of the Dyson from now on!

Ours did this we took it to pieces got a dust mask on and literally blew compressed air through it . Happens every 3-6 months dependant on how much really fine dust is clogging it