You are right... 90 to 95 is where it starts to work.. But most do not really take hold so you can hear them until 100 to 110.. Thats when they are engaged full.. You have to remember that the engine temp is not what the water temp at the point in the raidatior that the fan clutch is located behind... so the water temp will need to be higher to get the temp in the center area of the radiator that the fan clutch is behind up high enough to work.. Thats why the bi-metal is at a lower temp.. 73..

One thing you always need to remember about the engine temp.. Its the temp of the engine.. Not the temp of the water in the radiator.. In most all cases its far cooler..




Ken