Cooling is primarily a function of the mechanical fan, not the electrics. Especially when you have a problem at low speeds, that's where you start. The electrics are only a back up in case the system is on the edge of overheating. They should come on at around 105.

If the mechanical fan isn't engaging, then you have a problem with the fan clutch. I believe that by 89, all the 190's had viscous clutches. If this is the case, the only solution is to replace the clutch.