pencil plugs just need 12 volts. Any way they get the voltage is ok. The loop plug heavy wires will deliver the voltage. No insulators are necessary on the pencil plugs. Just make sure the ground wire is NOT used with the pencil plugs. If it is, that might account for the failed fuse.

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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