I've been asked to have a look at a DYSON DC01 hairdryer for a friend. She reports that when on full heat, 3 red lights, the machine runs for around 5 seconds then the 3 red lights flash and then the hairdryer stops working.
I've had a look at it and the only thing jumping out on me at the moment is the thermistor which tucks in just above the heating element. I've soldered a temporary thermistor from a set of GHD straighteners, rebuilt the hairdryer and tested it, hey Presto it works.
My problem is I don't want to run the hairdryer for too long with the temporary thermistor in case it blows something else.

Now a good Dyson thermistor measures 88.5 k ohms at 25 deg
The GHD one measures around 92 k ohms at 25 deg.

Am I correct in thinking they are both the same spec and I should be OK to replace the Dyson with the GHD or is there more to it than that?

 

Not the same specs, there's 4K ohms difference between them @25C, obviously it's an Ntc type so as it's getting hot the resistance goes down.
Can you replace it with the same thing.?

 

Not the same specs, there's 4K ohms difference between them @25C, obviously it's an Ntc type so as it's getting hot the resistance goes down.
Can you replace it with the same thing.?

Hi
I've never done a dyson hairdryer before and I don't know Jack about thermistors. Could I just get any 88k ohm thermistor and it should be good to go or do I need to take anything else in consideration?
Also is there any recommendations where to get them from, I'm in the UK.
Cheers

 

Thermistors are rated at @25C by their respective resistance, they all have a different temperature curve, so at say 20C it will be a higher resistance and a lower resistance at 100C, compared to others, so you can't just put any old one in, you have to put the correct one in. Try Farnells, RS, digikey..

 

Thermistors are rated at @25C by their respective resistance, they all have a different temperature curve, so at say 20C or 100C it will be a different resistance compared to others, so you can't just put any old one in, you have to put the correct one in. Try Farnells, RS, digikey..

Yeah I figured I'm missing something, the Hairdryer has 2 x 185 deg c thermal fuses, so I'm guessing I need a thermistor lower than that.if I was to buy say a 150 deg, 130 deg and possibly a 100 deg and trial and error until I find the right one that suits, there is no information out there to help me choose.
I've tried to reach out to dyson but all they say is I need to send it in and they will repair it at a cost of £100 all for the sake of a thermistor which will in reality cost 50p at most, I've asked them for the thermistor but they just put the phone down when I kept asking for the parts to repair it myself.

 

What you need to do is to measure the resistance at 100 C ( boiling water)and 25C and say 5C ( in the fridge) then look at thermistors on Farnells and Rs , they usually have a Steinhart equation chart for the thermistors, and this gives the values at each temperatures from zero to 100C , choose one that is best match.

 

What you need to do is to measure the resistance at 100 C ( boiling water)and 25C and say 5C ( in the fridge) then look at thermistors on Farnells and Rs , they usually have a Steinhart equation chart for the thermistors, and this gives the values at each temperatures from zero to 100C , choose one that is best match.

Oh wow, that's cracking advice. I will definitely try that tomorrow, thats exactly the tips which I can only get from someone who's got the experience. But thats the reason for me being on here, to learn. Shame I can't buy you a beer or three.

 

I can't seem to find any 90K thermistors, only 100K ones, see if any of these are the same physical size..it will work , I'm in the UK too.

https://uk.farnell.com/w/c/circuit-protection/thermistors/temperature-sensing-compensation-ntc-thermistors/prl/results/12?zero-power-resistance-at-25degc=100kohm&st=Ntc+thermistors&sort=P_PRICE

 

I can't seem to find any 90K thermistors, only 100K ones, see if any of these are the same physical size..it will work , I'm in the UK too.

https://uk.farnell.com/w/c/circuit-protection/thermistors/temperature-sensing-compensation-ntc-thermistors/prl/results/12?zero-power-resistance-at-25degc=100kohm&st=Ntc+thermistors&sort=P_PRICE

Yeah I was trying to find a 80k ohms but could only find a 10k, 50k and 100k ones. I’ve decided to get a 100k one and see what happens. I’m still going to do the different heat/cold test and see where that leads me too.
I’ve also had a look at the link you sent for farnells and it’s amazing how a shortage of components can inflate the price so much. Still better thank the £100 for Dyson to repair .
Thank you for all the time and effort you’ve spent helping me, not just on this issue but other post I’ve had on here too. Very much appreciated
This is the thermistor I have which fits into a plastic cradle which In turn fits perfectly into the Dyson.

 

Case style is D035,

https://uk.farnell.com/w/c/circuit-protection/thermistors/temperature-sensing-compensation-ntc-thermistors?zero-power-resistance-at-25degc=100kohm&thermistor-case-style=do-35&st=Ntc+thermistors&sort=P_PRICE

 

Case style is D035,

https://uk.farnell.com/w/c/circuit-protection/thermistors/temperature-sensing-compensation-ntc-thermistors?zero-power-resistance-at-25degc=100kohm&thermistor-case-style=do-35&st=Ntc+thermistors&sort=P_PRICE

Thanks Dodgydave, nowt dodgy about you though

 

I've just managed to get the Dyson HD01 working again. I did some research online, looking at different thermistors from different supplier's. After hours looking I came across some on AliExpress which I though I would try, I've nothing to lose for £2 for 20 of the 100k ones. After 9 days they arrived and just got around to fitting it yesterday, reassembled the Hairdryer and everything worked perfectly. I did rigorously test it for 2 hours. It is annoying though that the original one has its own carrier which I had to modify slightly to fit the thermistor, looks a little bit of a mess but ultimately works. Only time will tell I guess, but it's a fix for me and I've learnt so much about thermisters, and dyson.
The trickiest part for me was reassembly of all the wires, switches and the tiny circuit board back into the handle of the Hairdryer, just fiddly more than anything. So for the sake of 10p, maybe 2 hours work to repair and it's all working, rather than either £100 and sending it off to Dyson or throwing it away and cluttering up landfill. Why Dyson won't sell spare parts AND stop authorised repair outlets from repairing them is beyond me. Yes from a business point of view it's profitable, but surely it contributes to the mountain of otherwise usable products cluttering up our dwindling planet.
Anyway I hope this has helped someone in a little way, and I have to thank everyone for the input and advice given to me.

 

Hey Mick,

I am breaking down my HD01, the fuses on it aren't shorted out, it's cleaned to the bone, the only thing remaining is the thermistor, which I am getting a reading of 5K Ohms at 20C while I want to celebrate I found it, for a sanity check I put a 100K ohm resistor in series to see if it decides to turn on (It still remains the same, the lights come on, and immediately turn off in 1 second (The motor doesn't kick in or anything), is there a definitive way to rule in or out the thermistor?

My electronics experience is on the lower end of the side, these are things I read about in books, hands on time is pretty low.

 

Scratch that, the thermistor is okay after taking it out, reacts as expected. It's likely whatever is causing the buzzing noise. A fight for another day.

 

Scratch that, the thermistor is okay after taking it out, reacts as expected. It's likely whatever is causing the buzzing noise. A fight for another day.

Well, i have a few years experience with the dysons now, sonmy knowledge is a little better. I have found that the motor is more than likely the fault. The reason i say that is when there is hair wrapped around the shaft of the motor then it stops the motor initially spinning up and then it bells.out as a fault. You can either pluck all the hair out of the motor or burn the hair off with a hot air station amd a quick blow with a compressor or that can stuff.

Hope that helps

 

Well, i have a few years experience with the dysons now, sonmy knowledge is a little better. I have found that the motor is more than likely the fault. The reason i say that is when there is hair wrapped around the shaft of the motor then it stops the motor initially spinning up and then it bells.out as a fault. You can either pluck all the hair out of the motor or burn the hair off with a hot air station amd a quick blow with a compressor or that can stuff.

Hope that helps

I can't venture any further, as it's out of my knowhow. The PCBs being sandwiched liked that means I would have to desolder it off, a lot of room to make a mistake. This wasn't ever designed to be worked on when it was designed, it's sad that there aren't laws preventing companies from doing this. There even is an unused connector for diagnostics using their in house tools, not to require full disembody and save them time behind the cover plate.

I am placing an order for the entire upper piece off eBay next month, and see where it goes. The motor itself is spotless (I was supper disappointed, thinking that was the issue originally) I even tried spinning it and then powering it on but no avail.

https://www.ebay.ca/itm/353862864511