Smeg dishwasher drain pump not starting

[chris-uk]

Hi,

My Smeg dishwasher was stopping mid-program and after removing the panels, I found the drain pump to have burned out.

I replaced the pump with a new one and the new one burned out too after a week :^(

I've bought yet another pump and performed some diagnostics, prior to trying to use the dishwaher, as there's obviously another issue causing this.

What I've found is that the drain pump doesn't always start to spin-up properly. To prove this, I put the dishwasher on the drain part of the program and found that half of the time when I apply power, the motor spins-up properly, then other times, it just oscillates. Left in this oscillating state, it will just overheat.

It's as if a starter capacitor is failing. I actually tried changing the main capacitor, which is a cheap component, though it seems that the main capacitor is only for the washer pump, as this has made no difference.

I'm really scratching my head now.

Any ideas appreciated.

Thanks

Chris

[Andrew Gabriel]

They're usually shaded pole motors.

I wonder if it's driven by a triac which is burned out in one direction so it's getting DC (either when it should be off, or when it should be on, depending if it's an open or a short)?