I have been dealing with heat issues since I bought my jeep around 3 years ago. I got around to taking my center console out to check the duct that runs under the console that provides heat to the back seat. I wanted to do this first to check for leaks just venting under the console, and because I could feel very little air making it to the rear outlets in the console. Once I had everything apart and I could see how the duct runs I was able to make some decent hypothesis' about the lack of heat.
The first thing I can say is when the duct is in place nice and tight I still get almost no airflow coming out the rear of the duct to the back seat (no there aren't any clogs in the duct).
It also seems like the 2 holes that allow hot air out into the front floorboards are entirely too small. The amount of air that comes out (when the duct is in place) has very little volume and isnt moving fast. Way too much restriction.
So the last 2 mornings I have driven to work with the console and duct still removed and the amount of hot air that's able to flow at this point is phenomenal. My cabin was heated up within a few short minutes instead of nearly 15 minutes and just having it warm on the floorboard in the front.
I almost feel like keeping the center console duct removed is a better idea so that I have probably twice as much hot air flowing even though its just coming from the front. Like I said, it's incredible how much more hot air is flowing out with the duct removed.

Here is the duct:


So basically I just feel like that 90 degree bend is just a huge restriction and bottleneck keeping the air from having the proper volume flow.

The next thing I need to do is figure out how to get all that hot air into my cab when I put the console back in... without the duct. It may turn into some custom fab work and I lose the small tray at the front of the console so I can vent the air up through that or something.


Anyone else have any experience or ideas with this issue?

 

I will have to see what kind of airflow I get into the rear next time I've got the heat on. The only things that come to mind are possible blower motor efficiency and aftermarket t-stat that isn't keeping your engine as hot as it should be. Everyone I know with a 4.0 agrees with me that the heat will bake you.
I haven't got any ideas for new duct plans though.

 

I think I need to find a good way to get the duct nice and tight against the main outlet. That should give me the most pressure to my floor boards and out the back. Maybe it was just bad fitting before I took it apart. Maybe a couple rivets of it's possible. Or some gorilla tape. Good to 150° they say...

 

I've got a '98, so the duct to the rear vents is shaped a little different (I think). When I did my heater core, I beefed up the seal between the HVAC box and that duct with some stick-on insulating foam. I can still take it apart easily, I now get a better seal and more airflow to the rear. Here's a pic.

 

When I had to remove the console to put the heated seat switches in, I couldn't get the ashtray out with it in place, I had to
replace the foam seal there cause it just lost all the glue on it and would not stick anymore.
I just used something I had lying around.
But could not really get in around the duct on the heater box so put it on the inside of the duct under the console.