Yes I have plastic welded. I've never had success with my HF version. However, years ago I bought a plastic welder at a garage sale specifically sold for welding radiators, tanks etc. It looks like an electric soldering iron with a foot. The foot has a vertical tube attached about and inch high. You feed rods of plastic thru the tube where it gets heated, liquifies and flows out the bottom. I've welded quite a few things with it over the years. You have to match the plastics. The welding 'rod' is sold in rolls of different formulations. I mainly used it for welding plastic nubs on plastic barrels so I could install handles for carrying them when canoeing. I also repaired a few broked things over the years.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13