PreHeater Duct staying open
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Posting Guru
Joined: Feb 2007
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From: Wingo, Ky
PreHeater Duct staying open
I have noticed that even when the engine in my f100(73, 302) is up to operating temp that it is still breathing out of the preheater duct instead of switching over and breathing out of the fresh air intake hose. Would this be because of something wrong with the vac. temp switch in the intake manifold? Or the temp sensor on the top of the air filter cover? Thanks.
Postmaster
Joined: Jul 2001
Posts: 4,956
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From: MD
Sounds like the bimetallic sensor in the air cleaner gave up the ghost, which they all do after 30+ years. That's not good for the carburetor to be drawing in hot exhaust air all the times. Disconnect the vacuum line at the air cleaner lid and plug it so the flap will open for the fresh air from the outside to come in the carburetor.
Dunno if there's a replacement.
Dunno if there's a replacement.
Postmaster
Joined: Jul 2001
Posts: 4,956
Likes: 10
From: MD
Air cleaner temperature sensor. It heats up, closing vacuum from the manifold source so the vacuum motor will cease to operate, opening the flap.
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This original part number is for your application: 1973 F100 with 302 - D3ZZ9E607A.
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This original part number is for your application: 1973 F100 with 302 - D3ZZ9E607A.
Senior User
Joined: Nov 2008
Posts: 212
Likes: 1
How long should the door to the vacuum motor stay closed? Mine doesn't seem to open after the air cleaner horn becomes quite warm. Any way to inspect the bimetalic sensor visually/mechanically or to even salvage it?
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