indesit iwdc6125 jiggles but won't spin

[RamsayT]

I've had this indesit iwdc6125 for about 5 years, so I accept that it is getting a bit old but I would rather not throw it out if there is a fix:

Running a wash cycle on some towels it was getting towards the end when something happened and the RCD in the house tripped. Now I find that the washer won't spin the drum. It tries - you can see the drum torque a bit and then it gives up. Then it just makes a brief "electrical" noise and then stops again.

I have replaced the carbon brushes in the motor because that was easy and cheap. With the drive belt removed the motor seems to spin fine. If I run a spin programme you can hear the motor spin up to speed, stay there, slow to a lower speed and hold that, etc. so I think the controller etc. is all working fine. I can even load the motor a bit by pulling the belt against it and it keeps going. 

The drum seems to me to spin as freely as it ever did. It doesn't make any particularly horrible grinding noises when spun by hand, and it doesn't have the extreme movement front to back or otherwise that online videos of failed bearings seem to have, but I don't know how else to check that without dismantling the whole thing?

I can't see any obvious blown capacitors etc on the control board, nor any obvious burnt out wiring on the board or in the motor itself. I haven't seen anything that resembles a "starter capacitor" - do these even have one?

Any suggestions for further diagnostics welcomed - I don't want to buy a £120+ motor if that isn't the problem, and I don't want to replace the thing if a £20 bearing and some swearing would have it run again.

 

Ramsay 

[Whitegoodshelp (Andy)]

Hello Ramsey. Start capacitors are for induction motors. If carbon brushes are fitted, the motor is controlled by a module or pcb circuitry inside the main PCB. If brushes are ok and fitted the right way round and the motor won't run with a load in, there's possibly a fault on the motor armature or field coil, or a fault in the pcb. I don't think it's possible to work out which.

An engineer would try a new motor, and or pcb, and if that didn't work, they'd try the other. So it's not a DIY job, especially as it tripped the electrics. The motor could still have an insulation fault, but you can't test for that without a specialised Insulation test meter (washing machine is tripping the electrics)

The only other thing that could cause it, is if the drive belt is very slack. I have advice on how tight a washing machine belt should be here though a lot of belts can't be tightened anymore. Also, it would be obvious if it was the belt because you would be able to see and hear the motor slipping inside the belt.

If it tripped the electrics and fitting new brushes got the motor "running" again, it could need a new motor, but it could potentially also have damaged components inside the PCB. So I definitely recommend you do not speculatively fit any more parts.

 

[RamsayT]

Thank you for your helpful and comprehensive response!

The induction motor thing makes sense, so we can rule out starter capacitors. I'm not sure what you mean by the brushes being the right way round? The fittings are canted and the pre-cut slope on the graphite matches the curve of the armature nicely, so I can't see that any other way round would make sense? Plus, the motor runs fine without the drive belt. The armature and field coil windings look ok (except covered in some amount of graphite dust from the old brushes and my hands). The connector appears to have two wires to the hall effect sensor which I ignored, then three to the field coils, which show single digit resistances across all pairings, then two to the brushes which show single digit resistances which fluctuate slightly as you turn the armature but don't go very high anywhere noticeably. This suggests to me that the motor is probably ok (I'm typing this out as much for anyone who finds this on google as for my own benefit!). 

That leaves the control PCB. Once I got that out it does have some fairly horrible arcing visible (see attached), so that is probably the problem. I am unsure why the motor would run fine without the drive belt and then fail under load, but it certainly looks like the PCB insulation has been burnt away to form a channel, so it might insulate well enough without load and then arc when the load increases? The odd part is that, if I am following the wires correctly, that arcing is on the heater coil for the dryer. That makes sense as a high-power device that would fail like that; perhaps it leads to some earth/ground leakage when the motor part of the board is under load?

All this is far more interesting than just buying another washer/dryer, although perhaps I'm just delaying that :)

Ramsay

[Whitegoodshelp (Andy)]

Hi. You'd be surprised how many people fit the brushes the wrong way round so that only the back edge of the brush touches the armature. This causes it to run at reduced power and spark a lot. 

Armature can have little shorts inside the windings that make it labour under load but runs OK without load.

Your problem is that you do not have the tools to fix it. If the motor has low insulation it could have  low something in the module. If you for a new module it could potentially blow the new module. You need to test the insulation on the motor with 500 volts DC. 

[RamsayT]

Just as a follow up for anyone who finds this thread on google etc.:

I was able to borrow an insulation tester (contacts at a big University Electrical Engineering lab, definitely not a standard DIY option!). I get what look like fine readings at 1000V on all of the field coils, but the armature coils show 3Mohm (and the meter beeps very angrily) so it may well be that this is the problem? Or that might be normal for the brushes?

Anyway, I went quiet because some friends suddenly mentioned "Oh, we have a perfectly good washer dryer in the back of the garage that you can have" so the 'problem went away' in that sense!

Thank you for you assistance on this thread - if it had been a simple fix you would have led me to it. 

 

Ramsay

 

[Whitegoodshelp (Andy)]

Thanks for the update. You need to test the insulation only at 500v. Although it probably is the motor at fault. 

[RamsayT]

500V yields 4 and a bit MOhm on one brush and 5 and a bit MOhm on the other - vs 3.something at 1000V. (I used 1000V because... there's a setting on this machine for 1000V... ). This sounds to me like exactly what you were suggesting: insulation that works with no load but breaks down once there is a bit of build up. 

Out of idle curiosity - and, again, well outside of DIY repair: if one were to take the armature out and douse the coils in lacquer or varnish is this a problem that can be reduced/resolved? Presumably the fault is likely to be deep in the coil and they would need complete rewinding? 

 

[Whitegoodshelp (Andy)]

Aye most motors are welded together now so can't strip them down. Sometimes low insulation on a motor is a build up of carbon dust. But if it's  windings it's not something I've ever known be fixed.