White Knight tumble dryer - drum not turning

[powerstation]

Ah, that's a PSC (permanent split capacitor) motor. Low starting torque
but simple, cheap, and generally reliable.

using an electrolytic capacitor

 

[James Sweet]

using an electrolytic capacitor

If it uses an electrolytic capacitor that would explain why the
capacitor fails. Most of the dryers I've dealt with have oil filled run
capacitors, as does my drill press and the fan motors in my furnace and
heat pump, those are are all the PSC motors I have I can think of other
than the refrigerator compressor, dunno what sort of cap is in that,
I've never looked.

 

[powerstation]

If it uses an electrolytic capacitor that would explain why the capacitor
fails. Most of the dryers I've dealt with have oil filled run capacitors,
as does my drill press and the fan motors in my furnace and heat pump,
those are are all the PSC motors I have I can think of other than the
refrigerator compressor, dunno what sort of cap is in that, I've never
looked.

refrigerator compressors dont have a capacitor.

 

[James Sweet]

refrigerator compressors dont have a capacitor.

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]

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.

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

 

[Andrew Gabriel]

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.

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]

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.

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

 

[Guest]

It's either the capacitor itself, the starting switch if present, or a
fault in the motor. I'd check the switch first, if that works then
replace the capacitor, if it still won't start then it's probably the
start winding in the motor.

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]

When I take belt off the motor does not turn until I give it a
slight nudge. If I put the belt back on I still cant get the drum
to turn (probably because I cant turn it fast enough to start the
motor up).

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.

 

[Ron(UK)]

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.

There is often a thermal cutout embedded in the winding. The often fail
after repeatedly tripping.

Ron(UK)

 

[paulfoel]

OK. Changed the capacitor but now I cant get the motor to run at all
!!!!

Just to explain how its connected. From the switch/timer theres one
wire straight to the motor, and two to the capacitor. Then two run from
the capacitor to the motor.

The sole wire is live (I checked). What should be live into/out of the
capacitor. Why two wires in and out?

Should the motor run with just the one live? What about earth/ground?

Can someone explain whats what?

(BTW. Think I knackered the timer now though - shorted it and blew the
fuses etc.).

 

[Andrew Gabriel]

OK. Changed the capacitor but now I cant get the motor to run at all
!!!!

Just to explain how its connected. From the switch/timer theres one
wire straight to the motor, and two to the capacitor. Then two run from
the capacitor to the motor.

What you describe doesn't seem to have any neutral connection.
Are you sure you haven't lost a wire somewhere?
How many separate terminals are there on the old and new capacitors,
not counting multiple connections to the same terminals?

The sole wire is live (I checked). What should be live into/out of the
capacitor. Why two wires in and out?

Should the motor run with just the one live? What about earth/ground?

Can someone explain whats what?

Probably not without more info.

 

[paulfoel]

What you describe doesn't seem to have any neutral connection.
Are you sure you haven't lost a wire somewhere?
How many separate terminals are there on the old and new capacitors,
not counting multiple connections to the same terminals?


Probably not without more info.

What further info do u need?

 

[powerstation]

OK. Changed the capacitor but now I cant get the motor to run at all
!!!!

Just to explain how its connected. From the switch/timer theres one
wire straight to the motor, and two to the capacitor. Then two run from
the capacitor to the motor.

The sole wire is live (I checked). What should be live into/out of the
capacitor. Why two wires in and out?

Should the motor run with just the one live? What about earth/ground?

Can someone explain whats what?

(BTW. Think I knackered the timer now though - shorted it and blew the
fuses etc.).

The single wire from the motor on the white plastic connector is the
neutral, one of the wires to the capacitor should be live with the motor
running, these change over when the timer reverses the motor. What model do
you have, I will have a manual for it if you need it.

Peter

 

[William R. Walsh]

Hi!

refrigerator compressors dont have a capacitor.

Yes, quite a few of them do. I've seen a very few that didn't, but they
would be an exception to the rule in my view.

William

 

[BigGuyUK]

What further info do u need?

Sorry did not read all Post Yes it was the capacitor. As you say give the
motor a push and it runs This is what the capacitor does. Changed a few of
these over the past year.
BigGuyUK

 

[paulfoel]

The single wire from the motor on the white plastic connector is the
neutral, one of the wires to the capacitor should be live with the motor
running, these change over when the timer reverses the motor. What model do
you have, I will have a manual for it if you need it.

WV447

 

[paulfoel]

The single wire from the motor on the white plastic connector is the
neutral, one of the wires to the capacitor should be live with the motor
running, these change over when the timer reverses the motor. What model do
you have, I will have a manual for it if you need it.

So why 4 wires on the top of the capacitor? There are two on one side
of the top with a plastic separator between these and two more.

Should both inputs be on one side and both outputs on the other?

 

[James Sweet]

So why 4 wires on the top of the capacitor? There are two on one side
of the top with a plastic separator between these and two more.

Should both inputs be on one side and both outputs on the other?

There's probably two pares of terminals, with each pair connected
together. This is so you can connect more than one wire to each of the
two connections to the capacitor itself.

 

[Roland Butter]

Could this be the capacitor? I've heard that this type of motor uses
the capacitor to kick start the motor.

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.