You want to choose something like this:

https://www.amazon.com/Uxcell-500C-Temp ... B00PZO6XI4

The important words when searching for espresso machine wire are, high temperature and voltage, anything with automotive in the description will not likely be suitable. Also, actual high temperature rated crimp connectors are nickel plated steel, not brass or copper, though an espresso machine should not get hot enough to require those.

When I clicked on the link my Amazon account says: Purchased Feb 19, 2023. This is great wire to work with, much easier than the MIL-SPEC 22759 wire I've used in the past. This wire is 30C higher than the MIL-SPEC. Stripping insulation is a pain with the '759 wire because of being Teflon.

In the category of a lesson learned, I would not use any other wire than this, and I also like the McMaster Carr Hi Temp connectors I posted here. The label says to crimp, which popped out after the discussion with my electrician friend.

baldheadracing wrote:... I'll have to look inside my Club this evening (it is on all day today) to see if there is a similar pattern.

The 220 volt wiring from 1975 isn't in the greatest condition, but I don't see anything that shows one side is more affected than the other. (The power cord is new.)

I'v seen a few high power faston connectors fail in machines I've worked on for others and no wires, and I think (!) that crappy connectors are the key to the issue.

It's often more about it being the the wrong connector for the application than that they are crappy connectors.

true! I hate them everywhere though, many are loose-ish, insulation turning brittle in a year or so etc

They're loose because they are badly made or pure copper, brass or beryllium copper is way butter but more and much more expensive.

Looks like we all agree that using high quality terminals is the way to go for this application.

The OP mentioned using high temperature nickel plated steel quick disconnect terminals rated at 900°F (482°C) from McMaster-Carr. Because these terminals aren't insulated I'm a little concerned about using them for this application.

McMaster-Carr has fully insulated nylon plastic terminals with tin plated brass rated to 220°F (104°C). Is this suboptimal? If so, is there a better alternative out there? And if there is a better alternative, could someone post a link to a terminal that would work better?

For all my wiring if I am replacing it (even my smol guys) I use TGGT (Teflon Fiberglass Fiberglass Teflon) 14 AWG wire, good for 32.8A at 212F. It's not terribly expensive, but more than regular wire I see listed for sale using silicone or PVC plastics. I admit for my grounding wire I use silicone sheated wiring but it normally will not be drawing current. I source my terminal connectors from Digikey or Mouser depending on what else I'm purchasing at the time along with my power switches. I followed a marine (boat) electrician on his advice and use AMP PIDG connectors which have a higher temp rating than Nylon cheapies at Home Depot and related stores.
https://marinehowto.com/marine-wire-termination/

Among all of my machines I have not had a single issue relating to my connectors from a crimping perspective and no signs of melting or damage on any portion of my circuits due to my crimps. Machines like my President have been in total use for 1.5 years or more operating at 15A or higher. The crimp tool cannot be bought right now but it was among my best purchases I've made. If in doubt get a high quality crimping tool and not those cheapie hand crimpers.

14 AWG for 38A?

For reference, the National Electrical Code (NEC) notes the following ampacity for copper wire at 30 Celsius: 14 AWG - maximum of 20 Amps in free air, maximum of 15 Amps as part of a 3 conductor cable; 12 AWG - maximum of 25 Amps in free air, maximum of 20 Amps as part of a 3 conductor cable;

beware, that rating might be the current it can carry upon vaporizing, for continuous load I'd be far more conservative. It should work for many espresso machines, even at 110V.

I second buying a GOOD crimping tool, and where needed/possible one made for the connectors one is using. The difference between 'it looks tight' and 'it is tight' is hard to tell by looking.