AC Fan Dosen't Run - Page 1
Forum section: electronics / repair

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 08:12:07 am
content: Well this is fun, two things I like to use often have become broken to some point.Anyway, I have aACmotor from a fan that will no longer run, however the additional electronics seems to work just fine, that is after testing.This motor seems to have five wires, please see this photoor below.I have ran my multimeter in ohms mode and I think the motor itself is okay, and here is what I got...Between the wires:White & Black - 297ΩRed & Black - 0.257KΩRed & Blue - 27.3ΩRed & Yellow - 129.7ΩRed & White - 233.1ΩHowever, the start capacitor seems a bit off. Please see this photoor look below.Now it's labeled as a 2UF capacitor + or - 5%, well with how bad my maths is...2x0.05=0.10.1-2=1.9So, I am guessing that between 1.8 uF to 2.2uF should be okay, only when testing the start capacitor I was getting between 1.5uF and 1.6uF and no spark. Well at 450v you'd expect a spark.I was wanting to check to see if I was correct, before waiting until I get some money next and buy a drop in replacement capacitor.

author: Armadillo
author_rank: Super Contributor
timestamp: January 01, 2019, 08:17:35 am
content: The capacitor is OK.You can't rely on the component tester for any accurate result.The fault is obvious. Save your money on buying new cap.

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 09:10:15 am
content: Quote from: Armadillo on January 01, 2019, 08:17:35 amI did also use a capacitor meter and not just the LCR tester, which had the same resolute.So what is the fault?

author: Electro Detective
author_rank: Super Contributor
timestamp: January 01, 2019, 09:16:59 am
content: You really need an insulation/megger tester to track down issues with fans/motors.Also the capacitor may read ok but perhaps it's dropped it's mojo and just can't supply the goods anymore

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 09:28:24 am
content: Quote from: Electro Detective on January 01, 2019, 09:16:59 amWould attaching a variac to the capacitor wires to see if I can get the motor to spin for a short time, be a good idea?I was thinking setting it to 120v, since here in Australia we use 240v on out mains?

author: Dacke
author_rank: Regular Contributor
timestamp: January 01, 2019, 05:35:28 pm
content: That looks like a run capacitor, not a start capacitor. Start capacitors are much higher capacitance and are taken out of circuit once the motor is started. It's not like a room fan would need the extra torque from a start capacitor anyway. If you pull a run capacitor out of circuit, the motor should still operate albeit slower and less efficiently. The capacitor is probably fine.Those resistance values look very high for windings in a small fan motor, they should be reading almost zero.

author: Armadillo
author_rank: Super Contributor
timestamp: January 01, 2019, 05:46:40 pm
content: Agree, capacitor is OK, except for 68 watt fan on 230VAC, what do you expect the resistance to be?Quote from: Dacke on January 01, 2019, 05:35:28 pm

author: Dacke
author_rank: Regular Contributor
timestamp: January 01, 2019, 05:49:23 pm
content: For a small fan? Single digits on each winding has been my experience. Common to the highest speed winding would be the largest value.Edit - Just noticed but I think the bigger problem is that the white to black reading should be the lowest, with red to black being the highest according to the schematic. The readings taken are the opposite.

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 08:28:37 pm
content: So...White testing, I only tested the capacitor black wire and there are two black wires...To power the motor it has a four pin plug, and on that I am getting nothing...So, now I am guessing, the fuse inside of the motor has gone south?

author: Electro Detective
author_rank: Super Contributor
timestamp: January 01, 2019, 09:13:17 pm
content: Disassembly time perhaps...?

author: Microcheap
author_rank: Frequent Contributor
timestamp: January 01, 2019, 09:48:08 pm
content: These motors should have a thermal cutoff. I am guessing from the picture: testing the resistance from the input connector (black?) to the white wire should give you a small reading, if there's nothing, then probably the fuse is open.If you can open the motor it should be easy to test and confirm that.

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 10:10:23 pm
content: Quote from: Electro Detective on January 01, 2019, 09:13:17 pmBeen there, done that, its just held together with a few screws, thank god.Quote from: Microcheap on January 01, 2019, 09:48:08 pmYea, when I was trying to work things out, that is when I fell apart. I'm okay with brushed dc motors, since the two I dealt with had missing brushes, but this I am afraid of cutting one of the wires.After reading what has been said in this topic, getting a fuse and tapping in through the capacitor's black cable, in a sad attempt to jerry-rig the thing.I think I do know what happen, the pore wiring in my flat loosing it when I plug-in and fire up my air compressor x-x. Even the fuse in that thing was vaporized at some point.

author: floobydust
author_rank: Super Contributor
timestamp: January 01, 2019, 11:14:54 pm
content: OP, your ohmmeter readings do not add up? Red-White should total Wht-Yel and Yel-Blue and Blue-Red.Does this fan just hum, or need a spin to start or is it dead?

author: mictas
author_rank: Regular Contributor
timestamp: January 01, 2019, 11:33:30 pm
content: Quote from: floobydust on January 01, 2019, 11:14:54 pmDead, it dosen't make any noise.I did have an update, the plug that connected to the control PCB also has a black wire. When I was testing, I had tested between the capacitor's black wire and not the one on the plug its self.The plugs black wire, reads as NC... Yea, I should have checked that.Inside of the motor:

author: Electro Detective
author_rank: Super Contributor
timestamp: January 02, 2019, 02:47:42 am
content: Do the copper windings pass the smell test of minute doses of magic smoke released ?

author: Microcheap
author_rank: Frequent Contributor
timestamp: January 02, 2019, 02:58:59 am
content: There is your thermal fuse (see red arrow) remove it to test if possible.

author: mictas
author_rank: Regular Contributor
timestamp: January 02, 2019, 03:42:32 am
content: Quote from: Electro Detective on January 02, 2019, 02:47:42 amNope, no burning smellQuote from: Microcheap on January 02, 2019, 02:58:59 amThat I guessed, after I took the photo, but thanks for pointing that out.So, just cutting it out should solve it? (Well for test)

author: lwatts666
author_rank: Unknown
timestamp: January 02, 2019, 04:29:53 am
content: I know this is obvious, and you have probably checked this already, but does the rotor spin freely in its bearings? These small cap start motors have very little starting torque, and even stiff grease in the bearings can prevent them from starting.I just had a similar symptoms on a similar looking motor. The original lube had gummed up, making the bearings stiff, but not seized. Flushed out the bearings with kero and lightly repacked with fresh grease, now all good.

author: Microcheap
author_rank: Frequent Contributor
timestamp: January 02, 2019, 05:56:08 am
content: Quote from: mictas on January 02, 2019, 03:42:32 amYes you can cut it out, but for test purposes, maybe you can just follow the cables attached to its leads going to the connector and then test continuity from the plug. I can not see clearly from the pictures but I think you have one black cable coming from the connector, passing through the fuse and then another black (?) Cable connecting to the capacitor's terminal, so testing between these two points should answer the question.

author: james_s
author_rank: Super Contributor
timestamp: January 02, 2019, 06:01:22 am
content: Quote from: Dacke on January 01, 2019, 05:35:28 pmThat's not always true, the PSC motor is very common in AC units, both for the fan and compressor. These use a permanently connected capacitor to produce the phase shift necessary to make the motor spin. The run capacitor is a fairly common failure too, at least on the central AC and heat pump systems. They often use a dual section capacitor with around 5uF for the fan motor and 50uF for the compressor so that capacitor shown very well could be the run cap. The one in my heat pump failed over the summer on the hottest day of the year, the motor would just sit there and hum.Also those cheap component testers are surprisingly accurate, I bought one a while back expecting a gimmicky toy but it has really surprised me.

author: mictas
author_rank: Regular Contributor
timestamp: January 03, 2019, 06:01:07 am
content: Quote from: lwatts666 on January 02, 2019, 04:29:53 amYes the fan its self spins freely, I did also check the space between the magnet and coils, I found nothing to cause it to stop spinning.Quote from: Microcheap on January 02, 2019, 02:58:59 amSo I took off the cover and this is what I found.Quote from: Microcheap on January 02, 2019, 05:56:08 amThe photo above, shows what was hiding under the black thing. I still have yet to cut it out.But I wanted to ask, if I should put the two ends together to see if they start.A

author: Electro Detective
author_rank: Super Contributor
timestamp: January 03, 2019, 07:41:44 am
content: If you do decide to go that way, join them with a fuse that will cope with the start up and running current of 68 watts,stand back...switch onand don't forget to wear glassesif you haven't got a fuse, perhaps a 70 watt light globe as a joiner. Try a 60 and 100w if no love.You may have to do the guesswork for fuse values or globe, or both in series, I'm just guessing what I would tryEither way it's Safety Firstespecially on a possible bin candidate

author: mictas
author_rank: Regular Contributor
timestamp: January 03, 2019, 10:23:05 am
content: Quote from: Electro Detective on January 03, 2019, 07:41:44 amLets do math for a fuse?Okay, so we know that the voltage of the motor is 230v = V and power is watts = 68w and we go with P÷V=I68÷230=0.295So a 300mA 250v fast burning fuse?

author: Armadillo
author_rank: Super Contributor
timestamp: January 03, 2019, 10:32:31 am
content: It's a thermal fuse. The body is NOT conductive. No accidental electrical contact with anything resulting from vibration or abrasion.For trial test purpose, you can directly link the wire and taped it. The Ohms look OK.My advice is, don't put a fuse with exposed metal.Use a isolating transformer [not a variac] if you want. The KVA is limited.

author: mictas
author_rank: Regular Contributor
timestamp: January 03, 2019, 12:03:35 pm
content: Quote from: Armadillo on January 03, 2019, 10:32:31 amOh, my plan is to fuse the other two fans I own, so this doesn't happen again. But I plan to use one of three fuse holders.https://www.jaycar.com.au/square-6-3a-240v-m205-panel-mount-fuse-holder/p/SZ2034https://www.jaycar.com.au/low-voltage-10a-m205-panel-mount-fuse-holder/p/SZ2030https://www.jaycar.com.au/low-voltage-10a-3ag-panel-mount-fuse-holder/p/SZ2020And I have a few of these floating abouthttps://www.jaycar.com.au/standard-duty-5a-3ag-inline-fuse-holder/p/SZ2015BUT, how is my math for a 300mA fast burning fuse?That and I built a dim blub tester.

author: fzabkar
author_rank: Super Contributor
timestamp: January 03, 2019, 09:32:00 pm
content: Why not replace the thermal fuse with an automatically resetting thermal switch?For example, these devices are intended for use with battery packs, but they are rated for 3A at 250VAC:https://www.thermalprotectorsale.com/ts05-thermal-switch/These devices are specified for use in motors and lighting:https://www.thermalprotectorsale.com/kw-bimetal-thermostat/https://www.thermalprotectorsale.com/ts01ts02-bimetal-thermostat/You could choose a current rating of 3A, and place a second, standard, lower rated fuse outside the motor. In that way you could ensure that the external fuse responds to current faults while the internal fuse responds only to temperature faults.

author: Electro Detective
author_rank: Super Contributor
timestamp: January 10, 2019, 11:25:20 pm
content: Auto reset thermal fuse and standard fuse combo is a proven winnerSome high horse trotting soldering station manufacturers and their corpotrolls may wanna take notes herebut suggest strongly to rig up a SAFE, cheap (!) and easy way to pre-test the thermal fuse/s before install,taking into account the ambient enclosure temperatures to be expected under most operating conditionsi.e. installing the wrong temp value that heats up and cuts out at random on a hot day will create more work for you to troubleshoot and fix,with no fan to keep you cooland pre testing can help verify you haven't installed a dud from a bad OHL production batch,which lets you down, just when you really need it to work and cut out!

author: mictas
author_rank: Regular Contributor
timestamp: January 17, 2019, 12:44:58 am
content: Alright right then, I built up the nerve to try this and...I lost a 60w light globe, I forget I need to use a higher watt globe, to the load you are testing, my case it was a 68w motor.So, I cut out the fuse and soldered the wires together and after the first loss, I switched to a 75w globe, now when I tried to turn on the fan, it didn't run. But I got a glow from the globe... That I didn't take a photo of...So yes, I'm now at a loss on where to go from here and I didn't get any kind of moments from the motor.