This Repair Café took place at the Mountain View Senior Center from 11:00 AM to 3:00 PM.

First, I worked on an Instant Pot® Vortex® Plus 10 Quart air fryer that wouldn’t power on; the owner said it had just stopped working one day with no major incident preceding it. After some light disassembly (prying off the top vent and removing the top cover), we found that the bimetallic thermostat had been tripped and needed to be manually reset with a little button.

I’m not sure why the air fryer was designed the way it was, with a difficult-to-access manual-reset thermostat. If they intended for it to be resettable, I think they should have either put an automatic-reset thermostat, or else placed it in a more easily accessible place. If not, it would have been cheaper to put a thermal fuse.

Next, there was a pressure washer that wasn’t dispensing soap; the owner said he had put Dr. Bronner’s Liquid Castile Soap, a sort of all-purpose concentrated detergent meant to be mixed with water before use. He also mentioned that he’d brought the pressure washer to the Repair Café some months prior, where some fixers had partially disassembled it and then reassembled it, leading it to work once and then stop working again.

The soap was dispensed into the water stream using a venturi tube, which contained a small constriction used to create a pressure drop able to suck the soap in. There were also sprung check valves on the water and soap inputs to prevent back-flow, and, I think, to ensure that soap was only dispensed when the nozzle was opened fully, creating enough water flow to push the check valve open. Anyhow, upon fully disassembling the venturi, we saw some pasty greenish-white “stuff” which I cleaned out. With no garden-hose connection to test the pressure washer, I tried to simply blow through the venturi tube and put my finger over to the soap input to test for a drop in pressure, with limited success. Then we put the whole thing back together.

I am pretty sure that the issue did have to do with the venturi tube; the pipe bringing soap from the soap-tank to the venturi was not at all clogged, and the owner testified that the pressure washer worked just fine. However, I’m not certain as to why there was corrosion and whether or not my cleaning efforts did any good. I have three main theories as to the corrosion: 1) since the main body was made of aluminium and the soap-injector of brass/bronze, this may have caused some galvanic corrosion, especially since Castile soap contains plentiful ions, which clogged the valve; 2) soap scum may also have been a problem if hard water was used; and 3) perhaps the chloride contained in the soap caused bronze disease in the soap-injector.

Finally, someone brought a 4-slice toaster where the lever wasn’t staying down on one side. Funnily enough, when we took off the case, the problem didn’t occur. Thinking that the slot in the case was too short and obstructing the lever, I filed it down a bit, to no avail. The owner of the toaster suggested cleaning the electromagnet used to hold the lever down, but (to me) this made no sense since the electromagnetic force is a field force and doesn’t require contact. Then, thinking that the contacts were deformed, I tried to bend them up a bit, which predictably made the problem even worse — now, the levers wouldn’t stay down even with the case off. At this point, we noticed that the toaster wasn’t drawing any power even with the levers held down, meaning that they weren’t closing properly and the electromagnet wasn’t receiving any power. We noticed that the contacts had little strips of metal stamped out of them and bent upward that were the parts actually pushed by the lever, and that this strip on one of the contacts was too far down to work properly. However, bending it up simply led to it being deformed back down by the lever, and after a few cycles of this a crack appeared in the strip and it snapped. This was most likely the cause of failure — the electromagnet wasn’t able to hold the contacts fully closed, so as soon as you let go of the lever power was cut and the lever popped back up. That said, I’m still not sure why the symptom only appeared at first with the case on.