Block heater, if you have one, is on the opposite side of the block to the glow plugs. It has a 110volt cord on it that typically exits the front of the car. There is a block temperature sensor on the same side of the head as the glow plugs. This controls when the climate control turns on I believe. On some models there is also a temperature sensor that controls how long the glow plug light stays on.
It's highly unlikely you did anything to the block heater so you need to figure out what you actually did. Connector on the end of what wire broke off?

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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