Sounds like you have pencil plugs already. It should continue glowing after the light is out. You should be able to hear the relay click off. Does the small box the plugs are wired to on the firewall have an 80 amp fuse inside. If so, that's probably just the fuse box and the original relay is still functioning inside the car.

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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