Right, I said I'd do a proper write-up on dishwashers so here it is. These are one of my favourite things to buy broken and sell working because the margins are good and most of the common faults are pretty straightforward to fix. I'm talking about undercounter machines and glasswashers here, not the big pass-through and conveyor ones, that's a whole different thing.
In terms of brands, Winterhalter are the ones to look for. UC series undercounters and PT series pass-throughs. Built properly, parts are available, and a working one sells for anywhere between six hundred and twelve hundred quid depending on age and condition. A broken one goes for fifty to a hundred and fifty on eBay. That gap is where the money is.
Classeq are the workhorses of UK hospitality. Not as fancy as Winterhalter but they're absolutely everywhere, which means parts are cheap and every catering engineer in the country knows how to fix them. The Hydro range and the D500 are the most common ones you'll come across. Hobart machines are solid too, they last forever in fairness, but they're heavy as anything and some of the parts can get a bit pricey.
Anything else I'd be more cautious with. The no-brand ones from the catering catalogues aren't worth fixing because a new one is only a few hundred quid and you'll struggle to sell a used one.
So, faults. The most common one is not draining. Nine times out of ten that's the drain pump, either blocked with food debris or the impeller's gone. A new pump is usually thirty to sixty quid and it's about twenty minutes to swap. Dead easy.
Not heating up is the next one. Could be the element, could be the thermostat, could be the control board. Elements are cheap, maybe twenty or thirty quid. Thermostats are similar. Control boards are where it gets expensive, sometimes a couple of hundred depending on the model. If someone lists one as "turns on but doesn't heat" that's probably an element or thermostat job and well worth buying. If it doesn't turn on at all, could be the board, and I'd be a bit more careful about the price I paid.
Leaking is usually the door seal or the wash tank gasket. Seals are a few quid and easy to do. Sometimes the tank itself cracks though, and at that point it's basically scrap. Not much you can do with it.
The other big one is limescale. Machines that have been running in hard water areas without proper treatment get absolutely clogged up over time. Wash arms block up, the element gets coated, jets stop working properly. A good descale usually sorts it out but if the element's been neglected for years it might be too far gone, and that's hard to tell from a listing.
To give you a rough idea of the numbers, say you buy a Classeq D500 listed as "not working, spares or repair" on eBay for eighty quid delivered. You open it up and it's a dead drain pump. Forty quid for the part and half an hour's work. Clean it up, test it, and it sells as a working used machine for four to five hundred. That's a decent return for not very much effort. Obviously it doesn't always work out like that, sometimes you get one where the control board's fried and it's not worth the parts cost. But if you pick carefully and don't overpay for untested ones, the hit rate is pretty good.