Saved me from buying a new Dremel. I laughed for 5 minutes at the title of the video. I dropped mine when it was fairly new years ago. I put up with the vibration ever since. I just received a new armature and brushes today. Couldn't figure out the blue wire. With your help, I got it all back together. Runs like it was new (before being dropped.) I very much appreciated the resolution and clarity of the video. Being able to see the tiny parts is awesome. THANK YOU!

Thanks so much Dave, you saved me just 47 euros. My 4000 faltered when I was cutting dry wall on the ceiling. I thought it was due the dry plaster dust that moving parts were clogged. I opened it withou any DIY video's and I cleaned everything. But I couldn't get the two big brackets tight to each other again. The drewel after cleaning still had the same symptoms. The brushes by the way were looking good. I decided to check Amazon and other DIY stores and found one 3000 for 47 euros. Then I checked youtube just as a last resort and found your video. After that, I rearranged the red wire which was blocking and clamping the big blue on/off piece. I could now easily close it again. At first the drewel was still a bit coughing. I left it running at 30000 for a minute and now it is functioning smoothly through all rpm's. When I tilt the drewel when running at higher rpm it starts hampering a little bit, but I claim that to be the gyroprecession effects.

I don't usually take the time to comment, but you saved me a lot of frustration. I was in the middle of a job when I powered off my two year old Dremel. I came back to it and attempted to power it back on, but it was a DB as my grandfather would say, a Dead Body. I knew what it wasn't, but held off until I found a video before opening up this spring loaded contraption. Lo & behold, I opened it carefully and "upside down" and wouldn't you know my blue wire wasn't attached at all. Upon reassembly (thank you for the tips about guiding the various wires), she works and I can now stop cursing the name Dremel. Thank you once again for sharing your knowledge and being an asset to the KZfaq community as well as those into DIY.

Well done video. Great focus, framing, timing, length. Good explanation of the parts and pathways. The "resistor", metal can with the tapered plastic, is a "thermal fuse". They look like a few of the diode packages. When I worked at the electronics parts store, NOT Radio Shack, NTE (RCA/Philips/TCG) sells them for less than 20 cents each. Mine says 216C plus other things. That is a 216 Celsius thermal fuse. The same size device can be found wrapped in fiberglass insulation tubing buried within in most motors, coffee pots, toasters, etc. It may be tested just like any other fuse. ohm meter. beep = good. no beep = bad. They are crimp only. Soldering will melt the wax inside and ruin a brand new one. (Don't ask me how I know. lol. 3 tries later. The plastic bag they come in, comes with two brass crimps. Now I know why. lol.) They can handle huge amounts of current and voltage. Half a degree above the rating and poof, dead. I am not trying to be a know-it-all. Got an AA in Electronics. I'm like you. Love to take stuff apart and see which part I let the smoke out of.

You, mister, are a lifesaver. I stupidly took the Dremel apart, got everything mixed up and thought I'd need a new one. And then I put it back together with the aid of this video. Works perfectly, and even the bothersome screeching sound is gone now! Thank you!

I also done a dirty job. Done some artwork on a piece of slate. Then I cleaned the Dremel tool with an air matress blower . I think it blew the clip off. Grateful for guys like you Dremel tool pioneers.

Thank you SO MUCH for this video. My Dremel has been slowly losing power. I had just changed out the brushes but it sounded like they needed replaced again. When I opened up one side to look, the brush had been dragged into the motor and obliterated and the blue wire was out of place. I'm not sure if that's why the brush got sucked in, but if you hadn't posted this video, I would've never figured out where it went. I even looked on ereplacement parts for a tutorial and there wasn't anything explaining the wiring. You rock, thank you!

I had one of these apart after cleaning - and ended up not putting it back together for circa 1 year. This video was rather useful. Thanks & 73's de M0WUL.

Came here for the same reason, you sir are a saint, thank you for taking the time to share the knowledge

Thanks so much. I hit my glove with the dremel and it got wrapped up. It wouldn’t turn on after that. I took it apart and was able to tell the switch didn’t look right because of your clear video. Works like a charm now woohoo!

Awesome video. Thanks for posting. I only wish I checked Google/KZfaq before I wasted a good hour trying to figure it out. I left my 4000 outside, it rained, then wouldn't work. I made the mistake of not keeping Dremel side down when taking it apart, so guts stayed in the wrong half, pulling off both the red and blue wires. Don't bother calling the 800 number. Technician was useless. No, there wasn't a wiring diagram available, no there wasn't a colored picture of the internals, no she wouldn't tell me where that pesky blue wire went (I can't be the first person asking about it! But she did say something about liability... yeah, some product support! Was tempted to buy another, open it up, then return it... Anyway, back to figuring it out myself.) From bends in red wire, found the stator connection on the other side. And finally, from the blue bends, I saw that little depression under the brush. Your video was good to confirm that was the right place. Bad news was that I've lost speed control. Full speed only. So I guess after all this, I need a new board or whole new tool! Moral of the story... Don't get your Dremel tool wet! But again, video was very well done. Cleaning out the tool along with new brushes should extend the life, rather than just pitching it which I'm afraid most people will do.

Thanks you bro!!! , an hour with the infamous blue cable loose and without knowing where to place it, you are the best !!

I know this is 6 years old and you probably don’t read the comments anymore but you just saved the day! Thanks so much!

I think this is the most informative video I’ve ever watched. Your delivery is absolutely on point and when you are that thorough and having the demeanor you have, people that have a harder time learning something like this can retain it better. Great job 👏🏼👏🏼👏🏼 subscribed.

This video is spot on. Very knowledgeable, thorough, and breaks down every critical step, which reduces repair time, guesswork and frustration. Mine just took a shit one day seemingly at random, which was particularly disappointing because it was probably the 6th time I'd used it in the three weeks I had owned it. Apparently this little blue bastard became dislodged during use or a maybe I dropped it and don't remember. With the aid of this video i was able to tear it down, seat the wire, and lubricate and fine tune my Dremel 4000. Thank you for the very helpful video TXW5CSM.

Thank you for the great macro shots from above. It really helped with re-assembly and getting the wires routed the way they are suppose to be. Mine had a seized front bearing, which I was able to fix by removing its dust seal, blowing it out with compressed air, and re-lubricating. But it didn't run after re-assembly. Turned out the black coil wire connector had slipped loose, and it still looked connected! Others have reported that one tends to be loose from the factory. All is well now. Very helpful video.

Hi Dave, Excellent video and much appreciated. Due to one reason or another, the threaded shaft of my Dremel become burred and I was unable to screw on the collet nut. I was disappointed to find that this threaded shaft is part of the armature unit and has to be replaced as a whole unit. I was able to purchase a replacement part but was apprehensive about replacing it. After finding and watching your video, I am far more confident and informed now to handle the task. As you state, knowledge is power when it is shared and I truly am thankful you shared your knowledge in such a clear and informative way. Well done and Thanks again.

Haha ……. I was flummoxed as to how that wire attached to the brush casing and then I came across this fantastic tutorial ….. indeed sharing knowledge is a beautiful present 🙏 thank you very much

I know this video is old but today my dremel quit working and i took it apart and cleaned it all up then put back together and it ran like garbage, lo and behold that blue wire got me i really appreciate your video it was most helpful

Dude! I stared at that blue wire for 20 minutes until I thought, "Surely I'm not the first person to wonder where that thing came from". First search result... mysterious blue wire. Thanks man!

THANK YOU for the wire close-up. I screwed mine up on reassembly and this was very, very useful.

I've worked on my dremel 395 before...but the 'Blue Wire' on the 4000 had me stumped! Thank you so much for making this video. The video quality is the best I've seen on KZfaq. Your video was a life saver (or at least $149.00). :-)

Thanks. This solved my problem. It also is one of the most detailed, clear, and well done instructional videos I have seen on KZfaq.

THANK YOU!!!!!!!!!! This is just what I needed! I had wired it incorrectly. The little brass boxes on either side are where the carbon brushes sit. Figuring out how they plugged back in is the guts of disassembly. So glad you showed us how with clear visuals. So very helpful, very grateful!

Thank you so much sir! I had to shorten the power cable due to the individual wires sticking out of the cord, and after doing that, I was like "Where the hell did this blue wire come from?!'

Absolute hero. Cheers mate. Mine filled with tile dust so giving it a good clean out. Random blue wire panic over. Great vid with the zooming in and all 👍

Hi, THANKS A LOT. I happened to do very a dusty job ( taking out some hard set tile grout). That made the slide power switch got a bit stiff. So google - KZfaq and I land on this. First thanks for this. Short sweet and to the point. My Dremel 4000 ( European version) doesn't have the coil brushes installed the same way. You can't unscrew them. So all you do is take out the screws that hold the dremel halves together and pull the tops side( side from where the 5 holding screws are fitted) out. You have to be careful as the spring loaded plastic brush caps can fly out. I suppose ( in hindsight) you can put two fingers on them while you gently prise out the top half. Your video gave me the courage to pull my Dremel 4002 apart. Knowledge is power and sharing it empowers others. ..

Thank you so much for your kind thought of posting this video. I too found I could not fathom where this connector joined to, so you deserve a hearty thanks, and for your superbly clear instruction. Best wishes!

Thank you for the video! You´ve just saved me 105 euros for new machine.

I really appreciate this video! My blue wire clip wasn't in the place it should be, so the tool quit working after a few hours. When I opened the case, the blue wire was just there, not attached to anything.

Excellent video. You answered my "Blue Wire" question as well as the routing of the wires. Thank you very much for sharing your knowledge.

Mystery finally solved... Thanks for the very neat and structured walk-through!

Many thanks. I could not figure out where the blue wire went. Excellent presentation.

The title of your video couldn't have been any better! Thanks so much for sharing and saving me at least an hour today trying to put that Dremel back together!!!

God bless you!!! That blue wire was driving me nuts where did it hook to!! It is so WONDERFUL to SHARE knowledge my friend!! Thanks so much

Thanks for explaining this issue saved me a lot of heart ache.

A thousand thanks to you ! I've been searching where that blue wire needed to go for days after changing the speed variator of my dremel.I'm just putting a few french words here in hope that it will help Google bring people who have the same issue here."fil bleu du variateur électronique de la dremel 4000, composant F013400046"

I watched this vid about 2 years ago. All o had to tembrr was ‘blue wire goes where?’… thanks again.

Now, in dec 19, I had the same problem after cleaning my Dremel: this mysterious blue wire and its odd end with no place to plug it. I came to KZfaq and saw your video with this original and right title! Tks a lot, too and if you come to Sao Paulo I´ll buy you some Caipirinhas for these beautiful and on time help!

I had to clean my dremel, cause the power button got stuck from dust. I took the whole thing apart and couldnt get it back together and tried for probably an hour. The first two things you said after opening it were the Problem... Thank you so much, its working again now, and i know now how to do it!

When I disassembled the damned thing for first time I was about to throw it away in garbage. I thought there’s no way to put it back together... Then I saw the video and it’s up and working again. Thanks for sharing!!!!!

Thank you so much for your time and patience in locating where the BLUE WIRE is supposed to go. I had a dickens of a time trying to figure that one out! I have a call into Dremel for the fix and now I can cancel that.

Excellent video. Thank you so much for showing us where that elusive little blue wire goes. Now, I have more questions, like, how did it break free of its home in the first place? Crazy. It's so pinned in there you can't imagine it coming out of there. Thank you, again. Great video.

It's all in the detail and you've got them ALL covered with this tutorial - thank you - my 4000 is back to brand new again.

Thank you very much! I was exactly searching for where the blue wire sits!

Thank you for the video. I was certainly at a loss as to where that dang blue wire went.

Thanks for solving the mistery for me! In my case it still does not work though, it only starts when I hit it pretty hard near the brush on the opposite side of the speet potentiometer. Once started it runs. I tried to “kick start” it thinking it was a brush contact issue but no difference. I’ll keep diagnosing I guess! Thanks for the mystery solving!

Thank you thank you thank you. I’ve been sat here for at least a hour looking for where this dam blue wire goes to. I really had no idea so I thought KZfaq ! I probably would of still been here tomorrow looking for this and in the end I’d of just used it for spares and bought another ohh and that’s another thing don’t shot your old dremel away because you can use it for spares and repairs. The wiring was a little different in my dremel to the one shown even though it’s the same model. Must be down to the 240v system we have in the UK. I found a 0.3 mm drill bit inside the dremel and the rear bearing is rattling so it time I got a new one I think as the bearing is shot. Have no idea how the drill bit got in there though. It may be down to little fingers I think.

The blue wire conundrum! It was bugging me all day. Thank you. Nice hands btw.

Thanks to people like you i have learned more from you-tube than i ever did at school.

This was exactly the problem I ran into with my Dremel, fixed the problem with the blue wire today thanks to you, fantastic and thanks a lot for this inspiring video!

Thank you so much! I opened my Dremel up and the blue wire was free floating but I couldn’t find any information about where it was supposed to go!

Thanks very much for the well-narrated and informative video, it was critical in helping me fix my broken Dremel!

I was just watching this to learn how to disassemble my dremel and then I seen this blue wire and I was like wtf? And then I remembered the videos title lol. Nice work man!

Dude! You are the coolest! Thank you so much for making this video! There was no other reason for you to make this other than to be of help. And indeed, helpful you have been. Thanks!

I thought I'd broke it until I found your video. Thanks for posting a really good clear explanation.

You sir, are a gentleman and a scholar. Also, your video is great quality. Thanks for posting!

just a quick tip... take pictures whit your phone while you take stuff apart so you know where stuff goes when its time to put it back together. that would save you the 45 min it took to find the solution. it might seam a bit dumb but working whit computers this has saved me a loot of time.

Thank you very much for this video. I did grout work with my Dremel 4000 and wanted to take it apart to clean it and your video was perfect. Much appreciated Sir!

Thank you a lot man. Your video was very helpful for fixing my dremel. It was damaged when doing a cut on a bearing ring. A Little piece of plastic of the stator was broken, so I took all out, and found then difficult to re-assemble it again. So thanks again.

Thank you Dave. You are the man. Could not have done it without you.

Thank you! I opened mine apart and couldn't figure out where to put the blue wire. Turned out that still wasn't the problem. Some how one of the tabs on the housings for the brushes got bent. Bent it back into place and works like a charm now.

Whenever you take something apart take your time and take lots of photos from different angles. Also lay things out in the order you remove them and use a magnetic whiteboard for screws that way you can label them too.

Many thanks from Finland! The blue connector sprung off when opening my 4000 as well.

Great video! It answered all of my questions about the reassembly of this unit. Most importantly the mysterious blue wire/lead. Thanks!

Hi Dave found this today can't believe there was a video titled 'missing blue wire' which was exactly my problem all fixed now thank you

Cheers for the video - that blue wire is the exact reason why I watched the video :D

Thank you so much sir for uploading this. Video! I was going crazy trying to figure out where this blue wire went. 👍👍👍👍👍

Great info. I thank youfor making & sharing this with us, much appreciated.

Thank you for this. You explain all the items/steps really well!

Huge help, saved me a lot of heartache!

Thanks for the video. Bloody blue wire. Because of this video I managed to fix the Dremel. Had to pull it apart to replace the power lead. Cheers.

Following these steps didn't get her working again, but was a very methodical, detailed and practical vid. Very happy I watched and read the comments because Ed Ng's comment will be my next step in trying to un-shit my Dremmel. It died drilling a piece of fucking cedar!!!

thanks my friend, I order a new electric switch for my Dremel 4000 and I intent to replace it by myself, I believe the info provided here will be a great help, when reassembling the Dremel.

Its 2019 now, 5 years after you made this it helped me a lot! I was indeed getting crazy about the blue wire :-), My tool is working again thx a lot, if you ever come to Belgium I buy you some beers or other drinks!

I have never seen a video of this quality !! Great ++

Thank you men, you save my life, because i try to replace the thermal fuse and i accidentally move the position of the blue wire and in the moment to reemsamble i dont know where it was connect.

Thank you. I also wondering where that bleu wire came from. Your video was very helpful. thank you very much.

A+ tutorial: clearly discussed and pointed out. Thanks!

Awesome! Thank You! I thought it went there.. After I failed soldering it to the black wire. Hope I didn't F things up. We'll see.. Thanks for solving the blue wire mystery...

Thanks for a clear and well explained video. Though my Dremel is a different model, I still learned something from you. I have a later '400 Digital' model with an extra black wire (no blue like yours) and very different looking brushes. Just putting it out there - in case someone reads this comment - where does the spare black wire go? It has a slightly curved piece of copper on the end but there isn't any likely looking component it may attach to. I might do a question asking KZfaq video - does anyone do that?

You helped me. I needed to clean my dremel today. Thanks from Brazil.

Thanks Dave. You saved me from burning out the mother board. I did consider it may have been clipped onto the projecting diode as it appeared covered with a metallic coating. Again thanks

Thank you for this video. There is a part missing off of my dremel and I had no idea what to look for. Hopefully I can find it now that I know it's a brush cap and and know what to look for. Thank you again. :)

That is just what I needed to know, where the blue wire goes... thanks....

Omg thank you so much, I took mine apart last night and that blue wire was MYSTERY

I am impressed that you put this up. Thanks. helped a lot.

Thanks so much for posting this - much appreciated!

I'm just buying one of these and I'm already downloading this video to future purposes, I'm feeling that I'll need it someday.. thanks dude

Dude, this video was so helpful with the blue mystery wire! Thanks!

Thanks for this, just what I needed, my tool got a tad wet and cut out, took apart to dry out and yes that wire could not work out where it went until I saw this, thanks.

You Sir are a Godsend!! Many thanks for the video!

This was super helpful with the wiring in reassembly!

Thank you, Dave! It was very useful!

Blue wire is a feedback to the microcontroller .it has the functional role of keeping speed constant in rapport to the load at the shaft. On the brush you wil get an pulse at evey pass trough the rotor coils. This pulses are larger at low speed (les pulses per second) and when this happens at the same voltage given by the speed potentiometer witch is converted into voltage trough ADC from uC this pulse pin tell to the processor to increase the power at the triac. I hope I am clear enough and sorry for too deep details into controller board because this video is just for repair not development of better controller

Thank you for sharing this tutorial. Warm greetings and my respects from PR. God bless you.

Love the saying and love the video. I would have enjoyed the section on operation. Im sure someone familiar with the Dremmel would be bored but for those of us who dont know squat. We should be like a sponge to water, Keep Trucking..

Thanks mate, I'm from Mogi das Cruzes, São Paulo Brazil and I can tell you that I've not found any tutorial explaining this as his. Neither the Dremel itself. Congratulations and thank you for sharing your knowledge with us. Hugs! (Google translation)

Knowledge shared is power! Thanks for the video!

Very nice explanation! Thank you for spend and share your time. Excelent vídeo.