Gus Calabrese wrote: > I have not yet seen an explanation that is believeable. Oh dear! Was my explanation not believeable? Shall I try and re-state it stepwise? 1) The problem occurs mostly on outlets used for medium to high current loads. 2) By implication, it is caused by current in the circuit, not voltage across the adjacent pins. 3) Current causes *heating* in the contacts. The contacts are constructed from phosphor-bronze or similar material, tempered by the stamping process used to fabricate them. 4) Heating above a certain temperature causes annealing so that the contacts soften and the contact force decreases, raising the contact resistance. Heating of the chlorocarbon plastics used in plugs causes release of monomer and to some extent, free chloride which corrodes even corrosion-resistant alloys. 5) Loss of contact by these mechanisms causes further IÓR heating so this is a non-linear (compounding) effect. 6) The live and neutral contacts in the socket are *different* as the live goes to the switch contact whilst the neutral goes to a screw terminal where it is anchored to the incoming cable and in the case of double outlets, to the opposite outlet assembly. Consequently, the live contact is less firmly anchored and more likely to have poor contact in the first place. 7) A most significant corollary: The live contact is not heat-sunk by attachment to a larger area of metal including the incoming cable. Further, it is subject to aditional contact heating from any poor contact in the switch mechanism. In summary, it is little surprise that the live contact overheats by preference, *on a switched outlet*. I doubt you will observe the phenomenon on an unswitched outlet except *of course* where this is used with a previously damaged plug. Cheers, Paul B.