I have a pressure washer that I got as part of "a good deal", actually an exceedingly good deal as I later found out. I've had it a while, I guess probably at least 25 years, but it doesn't get used all that often. Hard to say, but I reckon I've probably not done 200 hours with it in that time - when I do use it, it tends to get used for a few hours at a time. But it's had the capacitor fail twice (I have a new one on the way).
The first time it just failed - carried on running and I recall noting a change in noise, but after stopping it it didn't start and just hummed. This time it failed rather more visibly ! In case it's not obvious, it's clearly overheated and melted plastic internally - there's a blob of grey plastic that's oozed out. Part of the "bog roll" construction has been pushed outwards a bit, pushing the potted seal out, and you can see the foil on the outer wrap of the section that's moved.
I've just replaced like-for-like (capacitance wise), but out of curiosity, does 40uF sound about right for this motor - it's capacitor run ? The plate doesn't give a speed.
This time while I had it open, I decided to draw out the circuit. I was surprised the first time I had it open to find what looked like a simple rotary switch and a small contactor in the box on front of the motor terminal box. But just looking at the wiring it seemed a little more complicated. So this is what I drew out :
I've assumed that the two terminals labelled O1 and O2 are a thermal switch embedded in the windings. The windings measured around 1.6R for U and 4R for Z.
But that bit with the NO contacts (13 & 14 on the contactor) and terminals 3 & 4 on the switch had me a little stumped (something along the lines of WTF is going on here went through my mind) until I got my multimeter out and had a closer look at the switch (rotary cam type). Then it made more sense. I'd assumed it was just a 2 pole on-off switch, but it isn't.
So that's a feature to prevent automatic start - either on power on or the thermal trip resetting. Terminals 3 & 4 only close while the switch is in-between the on and off positions, so closes momentarily while switching on to allow the contactor to close, after which it's help in by it's latching contacts. If power is lost or the trip operates, the contactor drops out but can't pull in again as 3&4 are open.
Like so many things, so simple and obvious once you've seen it, but it's not a configuration I'd come across before. Easy when you can build a cam switch for the job.
The first time it just failed - carried on running and I recall noting a change in noise, but after stopping it it didn't start and just hummed. This time it failed rather more visibly ! In case it's not obvious, it's clearly overheated and melted plastic internally - there's a blob of grey plastic that's oozed out. Part of the "bog roll" construction has been pushed outwards a bit, pushing the potted seal out, and you can see the foil on the outer wrap of the section that's moved.
I've just replaced like-for-like (capacitance wise), but out of curiosity, does 40uF sound about right for this motor - it's capacitor run ? The plate doesn't give a speed.
This time while I had it open, I decided to draw out the circuit. I was surprised the first time I had it open to find what looked like a simple rotary switch and a small contactor in the box on front of the motor terminal box. But just looking at the wiring it seemed a little more complicated. So this is what I drew out :
I've assumed that the two terminals labelled O1 and O2 are a thermal switch embedded in the windings. The windings measured around 1.6R for U and 4R for Z.
But that bit with the NO contacts (13 & 14 on the contactor) and terminals 3 & 4 on the switch had me a little stumped (something along the lines of WTF is going on here went through my mind) until I got my multimeter out and had a closer look at the switch (rotary cam type). Then it made more sense. I'd assumed it was just a 2 pole on-off switch, but it isn't.
So that's a feature to prevent automatic start - either on power on or the thermal trip resetting. Terminals 3 & 4 only close while the switch is in-between the on and off positions, so closes momentarily while switching on to allow the contactor to close, after which it's help in by it's latching contacts. If power is lost or the trip operates, the contactor drops out but can't pull in again as 3&4 are open.
Like so many things, so simple and obvious once you've seen it, but it's not a configuration I'd come across before. Easy when you can build a cam switch for the job.
