Parnall D59 dryer repair because it's blowing its fuse

[wobblewash]

This is my mum's Parnall D59 here in the UK (no date, but I think it's late 1950s/60s)

Recently it blew its fuse (13A one in the plug). Replacing the fuse and powering it on H3 (highest temperature) it started to spin up but after about half a second it blew again. We use an RCD at the socket but that hasn't tripped anytime (there isn't one in the house fuse box)

I'm a relative novice when it comes to electrics and see everything as an opportunity to learn (but I do know to be v. careful!) As I start to tackle this machine I'd appreciate any repair advice or head starts you might be able to give me.

The RCD doesn't trip, I think that means nothing is shorting to earth or current going anywhere it shouldn't be. Blowing the fuse would mean some component in the machine has died in a manner that it has no resistance.

The machine is relatively clear inside; I can identify a junction box, heating element, and a motor which drives the fan and drum. No signs of any burned cables or damage.

The fuse/RCD behaviour above might be enough for an expert to diagnose the fault.

For now my plan is to look at the junction box, check internals for health and no shorts (though this machine hasn't been moved in decades, and always left on H3). Then perhaps disconnect either the heating element to decide if that or the motor is the guity party. Any pointers appreciated! Thanks

 

[phillymatt53]

Check for free rotation by hand of the belt pulleys, perhaps some careful lubrication is needed of the bearings to insure that friction is not causing stress on the motor.
As for the heating elements, inspect for any wiring issues.

Others here might have some more advice.

 

[wobblewash]

Thanks, so I made some progress today. I'll write what happened here because it seems a bit inconsistent, I need to think about it.

Vacummed fluff out while visually inspecting everything. The motor does spin freely.

Inside the mains plug the live wire was very brittle; but still intact, no visual sign of an actual short But it needed a refresh so I cut the cable back and re-fitted it neatly.

Obtained a multimeter and tested the fuse (the second one) with it and found it to have not actually blown(!)

Tested for any shorts to the chassis with the multimeter, none found.

Disconnected the motor from the circuit and found 8.8 ohm of resistance across it.

Disconnected the heater element and found 47 ohm of resistance across it.

Started up the dryer with the motor detached and increased from 0-H3, and the heating element glowed orange by the time it was H3, with no fuse problem.

On that basis, re-attached the motor. The drum rotated with no fuse problem. Progress! I thought. But now finding a lot less heat (if any) from the element.

So all in all, it feels like some behaviour is inconsistent. I've left it to cool to try again and hopefully make it clearer if the heating element is working.

I can see the device that 'looks' towards the heating element (see the 2nd picture). I am wondering if this is a thermal safety cutout that's been triggered (or even a thermostat?) Perhaps I will try and draw a circuit diagram to make sense of it.