Not 100% sure if that was the purpose, but I recall seeing a ford pick up with a 7.3 diesel engine from Canada with an electric fan heather (squirrel cage type) fitted to the air filter intake hose for winter driving, That was the answer I got when asked about the fan, I saw the truck at the body shop about 2 years ago.

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2000 430 ML
2005 S500
87 300 D
61 300 restoring