A while back our dishwasher started making noises it shouldn't make. Inside an hour I had it removed from the kitchen, cases off and had found that a small plastic spoon had somehow made it past the filter and into the pump impeller housing. In order to get at the pump I had to detach some hoses which were secured with non reusable clips, so I refitted with Jubilee clips (not sure if this translates - image below), put it all back together, installed back into the kitchen and it's fine. Some may have replaced it; it cost me a few hours of time and a few scrapes on the hands and arms plus a couple of $ of clips. This is the first time I have ever seen the insides of a dishwasher, but it was worth a look.
Another one, this time on the car. A couple of years back the trunk lid on our Skoda Yeti failed to close. Slamming it made no difference - it just bounced without latching. It is one of those trunk latches with an electronic switch that operates the latch to open it. Only now, when you pushed on the switch you got a 'drilling' sound for a couple of seconds. So, apart came the trunk interior fittings and off came the latch. This is a sealed unit but I carefully prised it apart and found that the latch is opened by a small motor using a screw linear actuator (motor turns a coarse-threaded shaft - a captive slider moves up and down this shaft due to its internal threading). The shaft and slider are plastic and the shaft had sheared (hence the drilling noise as it turned, trying and failing to move the slider along the shaft). It fails in an 'open' mode though, hence being unable to close the trunk. I considered trying to glue the shaft back together but it was greased and I doubted I could make a good repair, so I ordered a new latch from Skoda and fitted it. A hour of my time, $40 for a new latch, all is well AND I now know how the latch works and have helped others who have had the same failure. At dealer rates that would have been $200 minimum.
I will happily disassemble pretty much anything to see if I can fix it. If not I generally learn about how it works.