White Knight tumble dryer - drum not turning

[powerstation]

refrigerator compressors dont have a capacitor.

[James Sweet]

Sure they do, they (again at least in the US) have a PSC motor in the compressor, usually the capacitor is 8-15 uF potted brick but I've seen older ones with oil filled capacitors.

[powerstation]

Not in the UK they are relay or PTC starters no capacitor

[Andrew Gabriel]

In UK, older ones used to have a start capacitor and relay (starter relay failing was a not uncommon failure mode in old age).

There's no externally visible capacitor in current models, but they are certainly induction motors of some type.

[powerstation]

Must be damn old I been working on them for 25yrs never seen one with a capacitor only a relay starter

[<me9]

They are usually two identical windings with a capacitor between them. The control box feeds each side of the capacitor in turn for a few seconds. This gives a few seconds of rotation in each direction. If the capacitor (or a winding) is open circuit, it won't start without assistance.

[Tony Williams]

That looks like the most significant paragraph in your original fault description.

It doesn't run until you poke it... which suggests that there is only a single phase connected, which could be power only to the Main winding or only to the Auxiliary winding (the one via the capacitor).

But even when poked it has no torque.... which then suggests that only the Aux winding is being powered.

It looks like it could be a poor connection to the main winding of the motor, or the main winding itself.

It's an ohmeter job. Locate and check continuity of the main winding, then work backwards along all wires and connections to it.

Perps, in order of probability:-

Any switches, switching or reversing power to the main winding. The main winding itself. Crimps and connections along the wiring.

If no obvious fault is found, do the same ohmeter exercise in the Auxiliary path, (just in case), particularly checking the capacitor for short circuit along the way.

[Roland Butter]

I had exactly this with a White Knight dryer. It was indeed the motor run (not motor start, apparently that's a different sort of motor) capacitor. I took it off (the big silver cylinder on top of the motor) and took it to a local motor rewinders where the bloke rummaged in a pile for a while and gave me a spare for a couple of quid.

That was ages ago and it's still running.

[Roland Butter]

Mine came from the tip 'cos the drum had broken away from the bearing carrier at the rear. Three small coachbolts and some nylocs and it's still going nearly five years later. Not bad for a condensing dryer.

On a related note, I notice that condensing dryers always score badly on energy consumption ratings, but I feel that's a bit unfair. We only use ours when it's too cold and damp to dry outdoors or on the rack winched up into the stairwell. In these conditions the heat from a vented dryer would be lost to the outside world whereas ours is kept in the house, usually on a day when the heating would be on anyway, so though it uses more energy and electricity isn't as cheap as gas, at least it isn't thrown away.

[J B]

Ours has now expired - drum won't turn anymore :-(

Spares or repair anyone?