Hotpoint W/M Motor

[gman76]

Hi All,

Have been looking at a w/m this evening that is blowing fuses, traced it to the main drum motor. I assumed it would probably be the start-up cap, however, I can't find one.

All I can see is two thinner (pink) wires that go into a metal housing at the inner bearing end. The resistance across these varies when the motor is rotated.

Can anyone explain to me what these are for?

Thanks in advance.

 

[zipper]

These motors don't have start capacitors. The two thin wires belong to the tacho generator, it supplies a reference voltage to the pcb which in turn regulates motor speed. The motor may have badly worn brushes which can cause fuses to blow. If the rcd is tripping there is an earth fault someplace.

 

[gman76]

That would explain it then.

There is no RCD, it is the fuse in the plug that is popping, has nearly taken a track out on the main PCB to.

I had thought about the brushes - the machine is 6 - 7 years old.

I'll check them out.

Thanks for responding.

 

[zipper]

Apart from popping fuses badly arcing brushes can also total your pcb. Best to park it up until you get the brushes checked out...

 

[gman76]

Well I've just taken all the skin off my knuckles removing the motor & it appears to be brushless!

Any other ideas?

S/c winding?

 

[zipper]

That's why it is important to post the model details. Bruised knuckles are a hazard in this line of work. Ok; so you have a brushless motor...most washer motors are universal type (brushes). Newer machines with brushless motors have a 3ph winding connected in delta with a capacitor across 2 of the phases. The capacitor is not mounted on the motor, it is integrated on the inverter card. If the motor windings have symmetrical resistance on all three phases then the inverter card is a likely culprit unless there is a dead short on the motor windings, which isn't that common. I suggest you post the full machine details to save any further speculation.

 

[gman76]

Tis a Hotpoint Ultima WM860, the (nearly) blown track on the main PCB is between the door switch & one of two black relays.

There are five wires plus the two thin pink ones feeding the motor.

 

[zipper]

Are you sure about the model number? I can't seem to pin it down. Have a look on the door sticker & post whatever is on there. The 5 motor leads are 3 feed + 2 klixon. The 2 pink leads go to the tacho gen. You should have symetrical resistance on the feed leads & more or less 0 ohms on the klixon. Not exactly sure what the tacho resistance is without identifying the model...it could be anything from 30 to a couple of hundred ohms.

 

[gman76]

Ooops! Sorry Zipper - it's WF860

Thanks again for ongoing help into the small hours!

Have just checked - I think I have identified the klixon terminals, indeed 0 ohms & 7 ohms across the winding terminals (all 3 in all combinations) & 114 ohms across the pink ones.

So I guess I'm looking at a PCB component failure then?

 

[zipper]

Nae bother
The readings you got on the motor sound about right to me. The partially blown track sounds more ominous. The door interlock is on J4 plug connection at the right hand side of the card. Terminals 5 & 6 on J3 (the plug connection directly below J4) are the heater, & the remaining 4 terminals on J3 belong to the pressure switch. I assume the 2 relays you identified are heater relay & motor reversing relay. The large black cylindrical object to the left of the relays is the motor capacitor.
Inverter capacitors can short out, so can door locks, pressure switches & relays. Heater elements have a tendency to go O/C or blow to earth.
The problem with Hotpoint pcb's is that if you buy a new one it doesn't come programmed. That means as well as having to buy the pcb you also have to shell out for a smartcard & card reader, which works out very expensive. I would speak to these people http://www.emwelec.co.uk/index.php?action=category&id=2&subid=28 They repair & supply recon pcb's. This has several advantages; It is much cheaper than a new pcb & they should also be able to identify which component has actually failed (so you can replace it before fitting the recon board). And a recon pcb doesn't need reprogramming. Note the full nameplate details & give them a call. For safety's sake I always change out the door switch when replacing a pcb. They don't cost much & it isn't worth taking a chance on blowing a new pcb for the sake of a £10 door interlock. One thing that is worth bearing in mind is that the motor could in fact read symmetrical resistance across all 3 phases with a multimeter but still have some kind of internal short in the winding (a multimeter only puts out a couple of volts). To test properly for internal shorts requires more specialized test equipment. Personally I think the motor is good & the blown track is caused by another component (cap, door switch, relay etc). Hope some of this helps....good luck

 

[gman76]

Thanks again for your in depth help Zipper - looks like my GF is going to purchase a new machine - at least I tried!!

Cheers!