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Old 10-23-2011, 05:30 PM   #1
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Heater challenge!

OK. I'm going to see if I can stump the Jeep braintrust. I've got a very strange heater problem. It blows nice and warm on the driver's side, but the air coming out on the passenger side is just whatever the current air temperature is. Hey, it keeps my feet warm, but since the wife rides shotgun I get a good griping about it from the right side. I've searched, and have seen a couple of others that have the same problem, but nobody knows the answer. I guess there's something going on in the heater box under the dash. Somehow could it be pulling in cold air after the heater core? Could there be a hole in the box? Or maybe the diverter that directs air over the heater core is only directing some air over the core, and allowing other air to bypass the core? I was hoping I wouldn't have to pull the heater box, but it appears that I will have to. Anybody have an idea on this?

Thanks.

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Old 10-23-2011, 06:06 PM   #2
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Is your vent door (right underneath the speaker on the passenger side) open or closed? Sounds like it's open. Sometimes I have to stick a pick or something of some sort to pull it closed all the way. I'd check that first if I were you. Good luck.

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Old 10-23-2011, 06:38 PM   #3
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dmblair is right on the money
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Old 10-23-2011, 07:37 PM   #4
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The vent door is closed. And both sides seem to be hot when using the defroster.
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Old 10-23-2011, 11:04 PM   #5
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You need to ride shotgun and see for sure where the cool air is coming from. I'd be willing to bet it's coming from the vent door there under the speaker. I'm trying to think of another way you'd be getting a split between the temps and that seems pretty much like the only way. Is the cool air coming from the exact opposite vent of where you are getting your heat on the drivers side? What I would do if riding shotgun isn't an option, park it and let it run til she gets up to temp. Turn your heater on and see if you still have the cool air coming out. If you do......then I'm out of ideas. If you don't, then you know it's a vent issue and not a heat issue. Good luck man, keep us posted on what you find.
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Old 10-23-2011, 11:47 PM   #6
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I've gotten under the dash feeling around with the heater hot and running on high. The different temps comes straight from the air deflector right in the center of the Jeep, directly in front of stick shift and under the radio, right where it blows out on your feet. The driver side of that deflector blows warm, and the passenger side of that deflector blows current air temp. I don't get it, because I thought that was nothing more than an air divider stuck on the end of the heated air path to split the air to both sides of the jeep. It seems both sides of that divider should be receiving the same feed of warm air, so I don't understand how one side can blow cool and the other hot. Doesn't make sense to me.
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Old 10-24-2011, 07:47 PM   #7
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OK. I think I'm figuring it out. I pulled the air divider off the heat box. When I stick my hand in the box, the bottom layer of air coming to the divider is definitely cooler than the top layer of air. I guess when the air hits the divider, all of the top air gets pushed to the far left of the divider, and the bottom layer gets forced to the right side of the divider. So, what's causing the cooler bottom layer of air? Based on this excellent thread:

http://www.wranglerforum.com/f8/yj-h...ned-68618.html

I believe I've got an idea. It must be 1 of 2 options. 1)My blend gate does not seal off completely at the bottom, and is allowing a smaller stream of air to bypass the heater. For whatever reason (maybe different velocities of the two air streams?) the air is not blending to one temp before reaching the divider. Now, I can hear the blend gate hitting the bottom of the box when I put it to warm. It sounds like plastic hitting plastic. Should the blend gate have some sort of foam around it to make a tighter seal?

Possible problem 2) Can a portion of the heater core clog up? Maybe one side is staying cool? Actually, as I'm typing this and thinking of it, that seems to be the more logical choice, since I hear the blend gate closing against the box. Both heater hoses get hot, so water is going in and out, but maybe its only circulating through one side of the core?
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Old 10-25-2011, 07:22 AM   #8
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With the way a heater core is setup I'd go with your option 1. With a heater core (I'm not an expert by any means and I'm horrible at explaining things) but isn't there just an inlet & outlet? If you're getting heat out of it then it shouldn't be clogged. There is only one way in and one way out, it really isn't split in half or anything like that...right? I'd try to get a look and see for sure what is going on with that blend door. Sounds like you've got a faulty seal or something.
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Old 10-25-2011, 08:18 AM   #9
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going back to the vent box theory, i've actually had to duct tape over the slits in the vent box as it never stayed completely shut. the driver side was nice and hot, the passenger side freezing...as soon as i "permanently closed" the vent no issues.....

oh, and the diverter under the radio sends air out equally in velocity and warmth.

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