the 1984 190 fan switch temp sender is the furthest rear sender of the three located on top of the engine by the top radiator hose. remove the single wire connector and ground it to the engine block with the car running, the fan clutch should engage spinning the fan. If not check all the fuses and check the connector at the fan clutch it is located on the drivers side by the water pump. you can also check the clutch operation by applying power to the fan clutch with a jumper wire..ENGINE AND KEY OFF!!!!! apply power to the clutch wire going into the fan clutch and see if you can spin the fan by hand. I would also replace the thermostat and use mercedes collant, no green stuff. hope this helps.
Joe