They're pretty standard. We used to buy from a specialist trade supplier and always kept a stock of several of the main values. The black one is 3 Minute rated ( is should be able to withstand mains voltage for that length of time 🤞) They do gradually lose capacitance over time but we've had motors that were 30 - 40 years old and the capacitors were still functioning ok.The grey one was fitted by the manufacturer in 1991/2 I believe. It died so I've been running the black one since. You'll see that it's a smaller capacitance value but is longer and slightly bigger diameter. The "worry" I had when I bought it (as a start capacitor) was that the quoted life was (I thought) quite short. So I bought two. So far so good tho' on that side of things.
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Electrickery
- Thread starter twentysix by twentyfive
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Looking at they drawing, relay coil is powered by the normally open ON switch . Your normally closed off switch completes the circuit once you press ON. Completes the path and your contacts switch over and power the motor. If your getting power out of the relay to the motor then , it’s maybe the capacitor start that’s not working . Unusual to be a motor shorting ? However any motors we replace at work are sealed units and only fault to the connections after which it’s replaced and sent away.Thanks @Tenkaykev . I got the plastic cover off and tried to find continuity through the coil. The little wires may be coated with insulation stuff maybe so I ended up on where they had been soldered on for a good contact. No continuity. The relay switches themselves move freely when pushed and I get continuity through those when held closed. So it seems it's the coil
For completeness I checked my original circuit diagram and realised I had drawn the relay switches between the wrong pins. With the cover off this was obvious so here's what it looks like now. All very understandable I think.
View attachment 610816
So thanks @Tenkaykev and @MrGrumpy for your assistance and patience with this old fart who's brain is turning to mush. Perhaps one last question if I may be so bold. Any thoughts on where I could source a suitable replacement (should Axminster PTC fail me)? What am I asking for?
OP
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twentysix by twentyfive
Clinging on tightly
- Location
- Over the Hill
I'm just waiting for Axminster PTC to get back to me first as, if they have the same old kit on the shelf it'll fit directly. I'm away next week so it'll be very quiet in here. If no response from Axminster when I get back I'll go down your route @Tenkaykev 
If the power is going to the motor then you would hear it trying to start, as the main run windings would be energised ( unless they are “ open circuit “ ) . The capacitor / start windings / centrifugal switch are taken out of circuit once the motor is up to speed, but the main “ run “ windings are always in circuit.
You do raise an excellent point though. On more than one occasion we’ve had a customer bring in a single phase motor thats not working. Our first step is to sniff the motor, there’s an unmistakable smell you get if the windings have burnt out. The second step is to look for the little red reset button that is sometimes fitted. It is a “ Klixon “ type of bimetallic button mechanism that snaps to open circuit on overload. A simple press and it resets. I’m assuming that @twentysix by twentyfive has checked that there’s no such mechanism on his motor.
OP
OP
twentysix by twentyfive
Clinging on tightly
- Location
- Over the Hill
I'm blissfully unaware of that. Also I have no sense of smell anymore. So I'll need A.N. Other for the sniff test and a I'll maybe have a hunt about for that mechanism.
