cross-posted from: https://lemmy.dbzer0.com/post/36272192
My washing machine is dying in stages. It started with the same symptoms as this thread. Specifically, after filling the tub for a wash cycle, it would go straight into a high-speed spin (full of water!) for a second or two (instead of the expected slow tumble), then quit. The speculation is that the tachometer is failing.
Then the machine got worse. I now cannot even start any program. No matter what program I select, I press start and after a few second pause the start button LED just blinks. It’s a generic blunt signal of a fault. The blinks are evenly spaced non-stop, so there is no error code of any kind.
To test the universal commutative motor, I followed the linked video and took resistance measurements. All seems okay in that regard (but this is based on vague resistance ranges that are not specific to my machine). Test results:
tachometer
Expectation: any reading that is not infinite/disconnected is fine.
- (video): 70 Ω
- (my motor): 52 Ω
carbon brushes:
Expectation: should be in the range 1—7 Ω
- (video): 5 Ω
- (my motor): 3.45 Ω
field windings:
Expectation: all combinations should be 1-7 Ω
- (video): 3.5 Ω
- (my motor): pin1-2: 1.35Ω, pin1-3: 1.35Ω, pin2-3: 1.9Ω
I do not have whatever model is in that video, but my readings are in the range suggested by the video presenter, fwiw. I believe my testing is incomplete because I was expecting the tachometer to be bad based on the behavior.
Motor spin test (hotwiring)
My next move was to try to make the motor spin. There is no service manual or wiring diagram for my Beko. So I inspected the motor and derived these pins (quotes are labels on the PCB):
1 (field) brown socket → brown+white “stator M” 2 (field) black socket → purple+white “stator 1” 3 (field) blue socket → red+white “commu” (commutator) 4 (brush) white socket → purple+yellow “rotor 2” 5 (brush) red socket → green+red “rotor 1” 6 (tacho) yellow socket → green “tacho” 7 (tacho) yellow socket → green “tacho” 8 (ground) green+yellow socket → green+yellow
Someone suggested this wiring:
L → pin 1
N → pin 5
jumper connecting pins 3 & 4I did not connect direct to the wall because I wanted to use the mechanical power button of the machine to turn on and off the motor (so I could quickly cut power if needed). So power took this path:
wall (220 VAC) → safety capacitor → mechanical button → motor (wiring redirected to motor instead of control panel)
When I switched it on, the motor spun for 1 or 2 seconds and I saw a white flash (I think) and the motor quit. I turned it off. Then tried to switch it on again. No response.
220 VAC quit coming out of the safety capacitor. Instead the voltage jumped around between 10 VAC and 20 VAC. So I thought I fried the capacitor or resisters therein. I checked the motor to see if any of the pins connected to ground (answer: no, so the motor was not harmed). Then I disconnected the safety capacitor and connected it just to mains and ground. 220 VAC was output (WTF… why does it magically work again?)
I think I’m back to the state it was in before I tried to power the motor. But I want to understand why the safety capacitor apparently flashed white and temporarily died with only 10—20vac output. I need to get to the bottom of this because I still need to test the motor for more than 1 second in a way that doesn’t cause more white flashes. Is it a bad idea to have the safety capacitor in the circuit?
I feel like if a motor is showing resistance properly, the “safety capacitor” is a spot I’d look, since caps can fail pretty easily, especially at 220vac. You’d just get a replacement and try that.
Right but I think that safety capacitor (SC) is the last thing I care about. IIUC, I could perhaps even simply bypass the SC because it’s merely improving the power quality/safety. It’s not worth buying an SC unless I can fix whatever is broken. If I could get the machine working, I could then of course consider replacing the SC as a final protective measure – but I’m not even sure anything is wrong with the SC.
The task at hand is testing every essential component of the washing machine, starting with the motor and tacho. I would like to understand what happened with the SC and motor though. Did I wire the motor wrong which caused the SC to flash and produce bad output for a moment? I don’t want to repeat that. I could power the motor directly without the SC, but if the motor is doing upstream damage then I guess I wouldn’t want my breaker box on the chopping block.
Possibly your motor is having an insulation breakdown when 220v is applied. Looks fine when testing with an ordinary multimeter and it’s low supply voltage.
So everything looks fine until it powers up and then you get a failure of the insulation on your motor windings, either failing to ground/frame or across windings in the motor. This flashover would likely fry whatever control components are in your main board, and it’s possible that your safety capacitor has a set of polyfuses in it that temporarily go high resistance when excess load is applied.
To check for an insulation breakdown you’d really need a megger which can apply 250/500v to the motor windings to check the leakage to ground/between windings.
Thanks for the feedback! So I guess I should buy a megger. Wow… not cheap. I think I see these at local 2nd hand street markets. I often thought “what strange multimeter… so few functions” but I didn’t realize what I was looking at. I will look for something that dials “500V” and has fewer modes than a multimeter, and ideally a “MΩ” printed somewhere although it looks like they won’t all print that on the device. I should probably learn how to test the megger itself so I buy something that works.
I suppose I could try to bring the motor into an appliance repair shop and pay them to test it with a megger.
As far as diagnosis of the whole machine-- suppose it’s true that I have an insulation failure. The control panel LEDs light up correctly when powered on, then when I try to start a program the start button just blinks. Does it seem viable or likely that faulty insulation would cause the controller to behave that way? I get the impression that the blinking LED means the controller detected an unspecified fault of some kind & refused to continue, which tempts me to think that the controller is functioning correctly – unless it’s a false positive of a failure.
I really want to avoid replacing multiple major parts because I don’t imagine I can return special ordered parts.
(update) At the street market I saw something like this for €100:
https://www.tekcoplus.com/cdn/shop/products/gain-express-gainexpress-Multimeter-SM-852B-set_1024x1024.jpg?v=1553658696
which was apparently a lousy price. I also saw a megger for €160 that looked kind of like this:
https://cdn.globalso.com/hvhipot/GD3128-Series-Insulation-Resistance-Tester2.jpg
I guess that’s what I need. It’s probably a good price for what it is, but not justified for my mission.
You can use a set of probes in series with a 100 watt incandescent bulb as a “poor man’s megger” to roughly check insulation. Of course everything needs to be appropriately insulated for this!
Remove the motor from the washing machine and place it on an insulating surface.
Put one probe from your light bulb on a motor terminal.
Put the other probe on the frame of the motor.
The bulb should not light up.
Repeat for various motor terminals in case there are different windings/etc.
I appreciate the guidance. But I think I can rule out insulation breakdown because I just removed the cover to the tacho generator and the ring magnet was broken in two pieces.
Hm that certainly won’t help!