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ACL Bimetal switch

sd_iconoclast

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February 17, 2012
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City, State
San Diego, CA
Year, Model & Trim Level
1991 Explorer
I have a '91 Explorer EB 4x4 5speed.
I am looking for a vacuum leak and I suspect the little temperature switch in the air cleaner. It is the thing that opens and closes the door that pulls hot air off the exhaust manifold.
I see this thing referred to as an "ACL Bimetal switch" in some vacuum diagrams.
It has two vacuum lines attached to it. One goes to the vacuum tree on the intake manifold. The other goes to the air door that switches between hot air (off the exhaust manifold) and cold air.
When I connect a hand vacuum pump to the intake side, I find that it will not hold vacuum. The air door diaphragm will hold vacuum.
Is my ACL Bimetal switch bad?
 






siguaw

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August 14, 2011
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City, State
Lynden, WA
Year, Model & Trim Level
1994 Ford Explorer 2 door
to find a vacuum leak. with engine idling just start spraying down all the vacuum lines with carb cleaner or break cleaner LIGHTLY. even WD-40 will work in a pinch. If you spray in the general area of the leak the motor with either rev up or die..
 






Jason94sport

Explorer Addict
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April 30, 2001
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City, State
FL
Year, Model & Trim Level
04 EB V8
That thing is pretty useless. You can simply pull the hose off the airbox & plug the hose with a golf tee or a screw or bolt.
 






awood

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February 15, 2006
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City, State
Kaysville, utah
Year, Model & Trim Level
94 XLT
I might be a little off here, but I believe the vacuum switch has a vent on it. The switch is fully "off" when it's warm, "open" when it's cold (allowing vacuum to the motor which opens the valve in the snorkel). Anything in between, and the switch will vent vacuum, which modulates the valve somewhere in between until things warm up fully.

If you're looking for a vacuum leak, just do as previously suggested and plug the line coming from the intake tree.
 






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