Haven't tried it with a cold engine but when the engine is warm, the fan stops right with the engine. It runs at about 83 degrees C down the road, a needle-width more with the a/c on. More than five minutes idling at 95 degrees F + with the a/c on and it'll get to about 95 degrees C.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo