This has happened to my fan several times. Each time, the problem was the 100 C switch that reads the coolant temperature. I can only tell you the location of it for 84 190's (it is in the housing that holds the water pump) -- they moved it in 85 to the other side of the block.

I have yet to experience a stuck relay (i have blown a couple of relay fuses). The problem has always been the same.

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Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi