My generator recently stopped providing AC power. I checked the breaker on the genny and it wasn't tripped. I opened up the splice box above the genny and measured 115vac. I figured out that the line from the genny came up under my dinnett seat where the power dist panel is located. I opened the space under the seat and found the transfer switch box. Upon opening the covet I discovered that both the hot and neutral splices from the genny line to the pigtails on the transfer switch had melted down due to poor connections. Pictures will follow.
I have worked with wirenuts, large and small for 50 years. They will work if properly installed and one of the more difficult splices to make is when you are joining 1 solid conductor to 1 or more stranded conductors. They ran 10/3 romex through sealtite flexable conduit between the genny and the transfer switch box. I'm guessing the transfer relay comes pre-mounted in the plastic enclosure and has #10 stranded wire pigtails already attached. The installer has to make wirenut splices to attach the "10/3 solid coach cables" to the pigtails.
Because we often use the full capacity of the 30 amp supply, those connections need to be close to 100% efficient. If the splice is loose or only a partial connection between the two conductors then the conductors will heat up due to the resistance when called on to carry a heavy load for extended time periods. I don't think I have ever found two blowouts like this in one junction.
To fix this and make it better than new I purchased new stranded pigtail leads with well made loop connectors already crimped on. (The damaged stranded pigtails were too short to cut off and reuse). There was plenty of slack to redo the 10/3 romex. I then made better splices using Grey size wirenuts. It all worked well when tested. I will be sure to check again after some long run times under a heavy load. The other 2 pairs of wires spliced to the other poles of the transfer looked to be in perfect shape and all screw terminals were tight.