Heater knobs operation - JeepForum.com

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post #1 of 5 Old 08-12-2014, 06:50 AM Thread Starter
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1986 CJ7 
Join Date: Aug 2009
Location: sammamish
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Heater knobs operation


I worked on my 86 CJ7 heater system last night.

The Air knob;

I pull half way out to "Heat" and I hear something operating but I don't see anything moving. ???

I pull all the way out to "Vent" and the door in the well between the hood and the windshield opens at the same time the door near the passengers feet open. ???

Can someone please explain the operation of this and does the "Temp" knob operate a flow control valve that allows water to flow through the heater core?


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post #2 of 5 Old 08-12-2014, 07:08 AM
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
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Half way let's outside air into the heater box so you have air flow to the feet or windshield as you move and gives the fan air flow so it can blow properly. This also helps keep a soft top inflated so it doesn't flap so much.
All the way out is the fresh air vent that opens by the passenger side feet and another flap up under for the drivers side feet. This bypasses the heater core area.
The heater control is a bypass flap. Coolant always flows through the core, the heat control just says how much fresh air either goes through the core or bypasses it to just blow outside air in when the air knob is half way.

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post #3 of 5 Old 08-12-2014, 10:33 AM
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This may help you.

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post #4 of 5 Old 08-12-2014, 02:48 PM Thread Starter
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1986 CJ7 
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Helps a lot. Thanks guys.
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post #5 of 5 Old 09-29-2014, 08:13 PM
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1972 CJ5 
Join Date: Jun 2014
Location: Lake Stevens
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Anybody have photos of a 72-75 heater box? Having issues with mine and would like to compare.
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