I didn't have time to read all 300 plus responses here but on a hunch I did an IR scan of my fuse Box this morning after a 20 mile drive to a job site.
I think if this had something to do with the design of the fuse Box that every vehicle made would show a heat signature at fuse 27. Mine did not. This leads me to think that this fix at the fuse Box may be nothing more than a band-aid.
I don't think that fuse should be getting hot in the 1st place, and on those vehicles that are getting hot... Something is wrong somewhere else that's causing it to draw too much amperage.
It's rare that I use my equipment for automotive applications but I thought what the hell. I do use it for commercial and residential electrical systems quite often. If this were an AC power system I could see a loose wire or bad breaker causing such an overheat but I'm skeptical of a design issue here because it would be more widespread. More importantly...it would be unlikely to be the same breaker on every vehicle since all of those small breaker sockets share the same design.
The hottest thing in this image are the 2 relays at the top at 139゚. That might be a little bit hotter than the water heater circuit breaker in your house for an electric water heater that's operating. My breaker 27 has virtually no heat signature. This is at idle after a 20 mile run down the highway. I have about 80000 miles on my 2014
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