Thermal Fuse for oscillating fan - Page 1
Forum section: electronics / beginners

author: BayouBoy
author_rank: Contributor
timestamp: July 14, 2018, 11:37:56 pm
content: Hi,I'm new at this fan troubleshooting and wondering if I can help help with a couple of issues. Fan stop working, but blade turns freely manually. Some quick research points to either a thermal fuse or capacitor. I wanted to be sure the attached is in fact the thermal fuse. Is there a way to verify if it needs changing before ordering the part? Also, would I need to find one with the exact printing as on the photo? Any help would be appreciated. Not sure of the fan brand name.. It's a pedestal type.

author: innkeeper
author_rank: Unknown
timestamp: July 15, 2018, 02:34:16 am
content: thats a non resettable thermal fuse by aupo, aupo is still in business, and the current model is the a4-f if I am not mistakenpretty easy to find, even on eBay and other outlets, and are really cheap.basically, the 2a is the current handling capacity, so certainly don't put in a 1a version, and the 130c is the temperature at which it cuts off and id sticks to that temperature.if you wanted to get fancy you could use a thermal switch, so once it cools down it would close again and you would not have to take it back apart to replace it.i happen to have a bag of 130C thermal switches in my parts bin, good for up to 8A at 250V . Id be happy to throw one in an envelope and send it to you if it would be of help.hard to tell if it would fit

author: BayouBoy
author_rank: Contributor
timestamp: July 15, 2018, 02:42:12 am
content: Thanks so much for the info...very helpful, especially for a newbie! In terms of the one you have fitting... the current one I sent a photo of is less than 1/4" square. Not sure what size yours is... the one in there seems to be a pretty tight fit. Let me know your thoughts.. if you think there's a chance of it fitting, that would be very much appreciated if you could send one. Thanks again.l

author: innkeeper
author_rank: Unknown
timestamp: July 15, 2018, 02:52:47 am
content: these are longer, I measure them at 1/4" wide by 9/16" long and 1/16th" thickwill it fitpart of the fun of fixing stuff is figuring that stuff out

author: amyk
author_rank: Super Contributor
timestamp: July 15, 2018, 04:21:28 pm
content: Check continuity both of the fuse and the windings.If the latter are open, you are not going to have an easy time repairing.

author: BayouBoy
author_rank: Contributor
timestamp: July 15, 2018, 04:29:34 pm
content: Hi,I think yours may work.. it's thinner than mine and the thickness may be more of an issue than the length.

author: innkeeper
author_rank: Unknown
timestamp: July 15, 2018, 09:17:18 pm
content: send me a private message with your address and i'll put it in the mail tomorrow

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:26:17 am
content: I bet you can make it work, it doesn't have to be an exact fit, just make sure it's in good contact with the windings.For testing purposes you can *temporarily* bypass the thermal fuse to see if the fan runs. It's possible and perhaps even likely that the capacitor failed causing the motor to not spin and that caused the windings to overheat. It's also possible a foreign object jammed it or the thermal fuse may have failed due to a power surge, mechanical damage or vibration.

author: innkeeper
author_rank: Unknown
timestamp: July 16, 2018, 03:52:41 am
content: i'll double down on whatjames_ssaid as the purpose of a thermal fuse or switch in a motor is to protect it from burning up. so make sure the thermal switches case will conduct the winding heat like the old one would have so it will open if it gets hot.As James said, you could bypass the fuse to test the motor, and likely its what id do myself to make sure the motor is otherwise functioning. But please don't run it that way permanently as its disabling a safety feature. That feature is there to keep worse things from happening, like potentially a fire or a meltdown.considering the fuse already went once, you have to ask yourself why it went in the first place, could there be something causing it to overheat that will happen again. If you happened to have an explainable reason, the fan was jammed, then you are probably in good shape.I also realized none of us actually answered your initial question, how do you know the thermal fuse needs replacing. its a simple resistance reading across the fuse, if its open, its bad, of its low/0 ohms it's good, and don't do that check with it plugged in. also if you bypass it, like James was talking about, the motor would work. that's also a way to confirm its bad.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 03:48:39 pm
content: I have had thermal fuses fail a couple times without experiencing overheating, and regular fuses fail sometimes without being overloaded. Vibrations, a being knocked over and whacking on the floor, or just normal thermal cycles can cause them to fail the same way solder joints occasionally fail.

author: BayouBoy
author_rank: Contributor
timestamp: July 16, 2018, 05:03:49 pm
content: Thanks for the input.. We recently moved so maybe banging around in the moving truck... Not sure about installing the new fuse.. Can I use crimpers to attach new fuse? And do I need to use some type of goop over the new install? There seems to have been some type of laquer covering the winding and old fuse that dried hard.. Since I'm new at this, not sure how important all these details are, but want to do it correctly.

author: innkeeper
author_rank: Unknown
timestamp: July 18, 2018, 08:52:44 pm
content: put them in the mailbox today.

author: BayouBoy
author_rank: Contributor
timestamp: July 22, 2018, 08:04:03 pm
content: Received your envelope yesterday. Just wanted to thank you for your kindness. Tried attaching using a crimp sleeve.. seemed like a solid connection. Fan still doesn't work.. guess it's time to find an electronics repair place. I learned how to take the fan apart and put it back together though

author: james_s
author_rank: Super Contributor
timestamp: July 22, 2018, 09:40:44 pm
content: If any electronics repair places still exist, they're not going to want to look at a fan. Unless it's a valuable antique there's no way that could be cost effective.You've come this far, dig in a little deeper and figure out why it isn't working. It's a very simple device and there are plenty of people here to answer questions.

author: BayouBoy
author_rank: Contributor
timestamp: July 22, 2018, 10:08:28 pm
content: Thank you for your encouragement. I generally stick with a problem til I find a solution...hate not having closure! I will take it apart again and take a photo of what I've done and post it here. I guess I was reluctant to ask for help, being such a novice, from the more knowledgeable experts on this forum. What I suppose I could try next would be to wire nut the 2 wires coming from fan and see if motor works..that will determine if it is in fact the fuse, correct?.. If it confirms it's the fuse, then my connection is probably faulty.

author: BayouBoy
author_rank: Contributor
timestamp: July 22, 2018, 10:22:34 pm
content: Here's what I've done thusfar.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 01:30:42 am
content: That looks reasonable at a glance. Do you have a multimeter? Do you get any continuity between the AC plug prongs? Does the switch work? Does anything at all happen when power is applied? Did you check the thermal switch to make sure it's normally closed and not normally open?

author: quinones
author_rank: Newbie
timestamp: July 23, 2018, 09:02:00 am
content: Check continuity both of the fuse and the windings.If the latter are open, you are not going to have an easy time repairing.

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 04:01:47 pm
content: Quote from: BayouBoy on July 22, 2018, 08:04:03 pmno problem at all. I am glad someone's getting use out of them. I will likely never use up this bag of them myself.your crimp job looks ok though I am assuming you stripped off the insulation on the white wires and crimped it on the wire and not on the insulation.I would do what the others are saying, do a continuity test. you will need an ohm meter for that, or, one of those cheap continuity checkers with the light bulb in it.sometimes the wire used for the motor has the enamel insulation on it, and if you happened to crimp on that, it won't conduct. that's just a thing to be aware of.if you don't own a meter, any cheap ohm meter will do for this purpose, even those cheap harbor freight ones you get for free with a coupon with any purchase.If you don't know how to do a continuity test, let us know, and we will walk you through it. Just don't do it when its plugged in ok

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 04:25:38 pm
content: Thank you.. I have the multi meter in the photo below, but not sure which setting it should be on. If someone could help with this, I can run those tests that were recommended. Thanks to everyone for the help. The display sometimes has a DC / AC choice depending on where the dial below is set

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 04:28:43 pm
content: You want it on the far clockwise setting, where the Omega symbol is, that will measure resistance.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 04:36:33 pm
content: OK...when I check the plug prongs it reads 0.L. When I check the fuse connections it beeps, then reads 0.0.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 04:42:39 pm
content: Sounds reasonable so far. O.L. means out of range, ie open circuit. The beep and 0.0 means short circuit (0 Ohms) which in this case is what you want a good fuse to be. Now you need to find where and why the circuit is open.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 04:44:28 pm
content: OK.. next step?

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 04:48:54 pm
content: was the fan switch in the on or off position when you tested the prongs?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 04:49:48 pm
content: Start breaking things down into smaller sections (mentally) and test those. Follow where the wires go, draw a schematic on paper if that helps. Try checking continuity between each plug prong and whatever the other end of the wire connects to, check across the switch with it both off and on, you should see OL with it off and 0.0 with it on. Somewhere along the line you'll zero in on the open circuit. It's like locating a kink in a garden hose, you look at one part of the hose and see that it's plump so the kink must be downstream. You walk around the corner and find limp hose, so you start moving inward from each end until you find the spot where it changes from plump to limp and that's the clog or kink.

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 04:57:09 pm
content: let us see which wire is not conducting, with the fan in the on position, do a continuity check from the thermal switch to each prong, my guess is one will read 0.0 and one will read o.l.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 04:58:52 pm
content: I tested the prongs with switch on , then off... same reading 0.L. Also, not the type of plug that has a fuse in it.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 05:01:58 pm
content: Well keep checking things, with the switch on you should see continuity between the plug prongs, probably not 0.0, but not OL either. Somewhere you've got an open circuit, just keep narrowing it down.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:05:28 pm
content: With switch on... one prong on thermal switch and one on prong. One prong reads 0.L, the other reads 294.0

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:12:00 pm
content: How will I know, based on the reading, when / where the short circuit is?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 05:12:32 pm
content: 294 sounds like the resistance of the motor windings so that's a good sign, it means the motor is probably ok. So now what is between the points where you measured OL? The fault is somewhere between those two points.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 05:13:50 pm
content: The problem you have is not a short but an open. Open on your meter reads O.L., if you get that between any two points in the circuit then the fault is between those points. Anything other than O.L. can be assumed to be ok for the time being.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:15:06 pm
content: The O.L reading was when I had a meter probe on each plug prong

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 05:17:28 pm
content: Well, work your way up. Attach one probe of the meter to one of the plug prongs and keep it there for now. Follow the cord to the other end and touch the other probe there. If that gives you a reading then move to the next node and try there. You need a complete circuit from one plug prong to the other and somewhere along that loop you have a break.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:25:01 pm
content: OK... I checked everywhere I could find a connection.. one probe on connection and one on plug prong. The only place I got 0.L was green/green & yellow wires (see photo). All other readings were 0.0.

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 05:40:33 pm
content: the green wire is typically the ground wire, and the white and black go to the prongs. check to see if that white wire is connected to the prong you are getting the O.L. reading on to the thermal switch when the power switch is on for the fan bu doing a continuity check from that white wire to the plug.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:47:38 pm
content: The white and black are crimped together, so not sure how to separate so I can test just the white. But... with switch on, one probe on black/white connection and one on plug prong, I get reading of 336.0

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 05:49:45 pm
content: you do not need to, just test from the point they are connected together to the plug.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:51:32 pm
content: Ok...that's what I did. Got a reading of 336.0

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 05:55:10 pm
content: there are two prongs. give the reading to each individually.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 05:57:41 pm
content: Oh, sorry... one reads 336.0, the other 0.L

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 06:04:20 pm
content: ok so, the 336.0 is going up and though the motor.the 0.L. would then be the connection out to the plug.it sounds like you have a bad power cord.lets double check, turn the fan switch off. then measure again from the white/black connector to each prong.my guess is both prongs will now read 0.L.if so, you have a break in the wire someplace between the white/black connector and the prong.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 06:08:54 pm
content: You are correct.. with switch off, both prongs read 0.L. How can there be a break in the power cord, wires are insulated and in one piece.. If that's the case do I need to just replace the cord?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 06:13:19 pm
content: Wires can and do occasionally break inside the insulation. Let's do a few more checks to be sure though, measure between the crimp connection on the white wire and the plug. If you can't get a probe up inside the crimp cap you should be able to poke a paperclip or pin up in there to contact the bare wire.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 06:15:13 pm
content: That was the test I just did.. Am I misunderstanding.. see previous post where both prongs read 0.L

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 06:16:58 pm
content: yes, ... but I've found that many times the wire breaks either right at the point it enters the appliance or right at the plug. so many times I can just cut the plug off and hook up a new 3 prong plug from my local home supply.since the cord is bad anyway ... you could do further testing by cutting the power cord an inch or two away from the plug and see if you get conductivity on the white wire to the white-black connection. if so, you could try and replace just the plug instead of the wire and the plug.or just go get a new plug and wire and have done with it

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 06:19:35 pm
content: One of my favorite tricks for locating a break in a wire is to connect it to a neon sign transformer and see where it smokes. Obviously not something I'd recommend for a beginner though.

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 06:21:38 pm
content: Quote from: james_s on July 23, 2018, 06:19:35 pmsounds like fun! .. but yea lets not give him any bad ideas

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 06:24:39 pm
content: OK..I cut the plug off and tested from black/white wire crimp to bare cut white wire.. still reads 0.L.. So replace power cord with new one that has same color wires (green, white , black)? Oh, and do I need new crimps or can they be reused?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 06:33:31 pm
content: It doesn't matter what color the wires are, but black, white and green are typical. If you cut the end off one of those power cords used on computers occasionally you'll find the European brown, blue and green.You can't reuse crimp connectors but you can replace them with small wire nuts if you prefer.

author: BayouBoy
author_rank: Contributor
timestamp: July 23, 2018, 06:35:35 pm
content: OK...thanks a million to all that helped.. It's been an education.. Will let you know when power cord is replaced and if problem is solved!!

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 06:38:12 pm
content: yea USA colors are white for the return, black for the hot wire, and green for earth ground.

author: innkeeper
author_rank: Unknown
timestamp: July 23, 2018, 06:42:39 pm
content: home depot sells chords like this

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 09:00:31 pm
content: If you have a thrift store or computer recycler nearby you might pop in and see if they have any computer power cords, those tend to be cheap and plentiful since so much stuff uses them and you can cut the end off and get a universal replacement cord.

author: BayouBoy
author_rank: Contributor
timestamp: July 25, 2018, 01:43:27 am
content: Hi again,Got the replacement power cord and started to disconnect then noticed the black wire coming from power cord goes to the switch (see photo). Not sure how to disconnect and reconnect?? Help again appreciated :-)

author: innkeeper
author_rank: Unknown
timestamp: July 25, 2018, 03:15:31 am
content: hmm.. good question...you could try and disassemble the switch and try to reconnect it the way the original or cut the wire and connect the new one in like the white wire is connected.personally, i've not seen a switch exactly like that, so I have no idea what you're going to get into if you try opening it, or even if its some sealed unit.So, if it were me, id just cut the wire with enough room to comfortably connect the new chord to it and connect the new one to it.opinions anyone?

author: james_s
author_rank: Super Contributor
timestamp: July 25, 2018, 07:33:55 am
content: Sometimes there's a place you can poke a wire in and release the terminal, other times it's crimped to a contact inside the switch. Don't try to take the switch apart, it's likely to go BOING! and you'll never get it back together right again. Just cut the wire off far enough from the switch that you can splice it using the method of your choice. Crimp butt splice, crimp cap, wire nut, solder and heatshrink, just whatever you're comfortable with that will fit in the space.

author: BayouBoy
author_rank: Contributor
timestamp: July 25, 2018, 05:29:20 pm
content: Success! Thanks to all again for your patience and guidance..

author: innkeeper
author_rank: Unknown
timestamp: July 26, 2018, 02:00:12 am
content: awsum!

author: BayAreaElectroNut
author_rank: Newbie
timestamp: June 28, 2021, 07:12:07 pm
content: I know this is an old topic but it was still relevant and useful in 2021.My Holmes pedestal fan died after running slower and slower over a period of months.I took it apart and found that the "bearings" had too much friction in them. Basically, I should have added some 3-in-1 oil lubricating oil to the shaft that was running dry in the sleeves. The back bearing is easy to access, the front one is hidden inside the metal front cap, I would have had to just spray and pray with some spray lubricant (not WD-40).Anyway, the motor was dead and not turning even after the load had been removed.I cut up all the wires and finally noticed the little AUPO A4-F thermal fuse buried in the resin in the windings. Its showing infinite resistance (open).If I had discovered this post earlier, I might have been able to save the fan but unfortunately, the circuits and wires are in absolute shreds !I wanted to add a delayed Thank You - the device is indeed an AUPO A4-F 130C 2A fuse in the Holmes pedestal fan.

author: james_s
author_rank: Super Contributor
timestamp: June 28, 2021, 07:27:47 pm
content: Yes, running slower and slower should have told you that something was seriously wrong and needed attention. A little light machine oil in the bearings would have gotten it going again no problem. Better motors even have little tubes you are supposed to put a few drops of oil in yearly.

author: bob91343
author_rank: Super Contributor
timestamp: June 29, 2021, 05:51:35 am
content: Not long ago my daughter complained that her little fan wouldn't run. I found the bearings dry. So I put some oil on them and it spun nicely. Plugged it in, and it worked fine. I gave it back to her and later asked if it's okay.She said it's perfect, and no longer makes the loud noise it used to make before it quit.