I was able to rule one or two more things out this weekend. I removed the blower/motor from behind the glove box and it runs fine at any speed. So I can cross the blower and blower resistor as possible causes off the list. Checked the cabin air filter - a little dirty but not clogged so bat air would be blocked.

With the glove box off - I did notice that what I'm assuming was a blend door (just above the cabin air filter with a honeycomb grate) opened and closed freely. It's opened, and then closes when I start the car - looks like this is the blend door that controls recirculated air vs the vent. The one under the steering column works also so one more left to inspect...

 

Seem to have fixed the issue. There is an actuator on the driver side, right of the pedals not too far up the center console you can reach w/o much trouble. This one was turning, but from what I read, this is the one that controls the AC/Heat blend door on the Liberty. I removed just to make sure it was working correctly - it's just two star head screws, pretty good clearance except for a few cables hanging down.

Once I removed the actuator I tried switching from heat to AC and back. When switching to AC - the actuator turned a couple times - when I switch back to heat however the actuator barely turned and kind of stuttered. I opened the actuator and looks like a few of the teeth had broken off one of the gears. Luckily you can turn the blend door by hand and as soon as I did I got full heat - back to normal.

Here are a few pics (broken gear on the opened up actuator - top right) - the part is about $37 - I could probably change the little gear, but sure it'd be more trouble than it's worth to find the right sized gear. It's not technically fixed - but isolated the problem and hoping for an easy part swap. It's stuck on heat until I manually turn the blend door or get a new motor - but it's cooling off in the Carolina's now so it works for me!

 

Nice sleuthing. Well done. I will definitely keep this solution in mind if my heat or A/C ever starts to act up.

 

I just bought a 2008 , drove it home tonight.1 st thing I noticed is no heat or next to none. I have checked the things you have stated here. I have not flushed the heater core. The heater hose going to the heater core is hot the return hose is warm. This seems to indicate to me that there is some heat transfer from the heater core. The blend doors behind the console are both working the bottom one looks to control the heat and the top looks to control where the heat comes out. Floor ,dash,defrost. Other than the heater core being plugged up ,I am not sure what to check . Anything else?

 

Not an expert by any means - but from what I've read on different forums/seen on Youtube there are commonly a few things it could be.

This is a video of what i checked - you can remove the actuator with two screws - and turn the blend door by hand to see if it's stuck and or actuator is broken.

If your AC and heat are blowing on and work at variable speeds - it would appear the blower and blower resistor are OK. If it works on different modes, your climate control knobs are probably OK too.

There are a few fuses you may want to check in the PCM - it's easy to rule a blown fuse out. I don't know the numbers off hand but they should be listed on the case to the PCM.

You can check for trapped air in your cooling system pretty easily - you can find instructions online if you don't know how. Also making sure coolant isn't low.

If heat is blowing but weak the heater core flush might be worth a try - I've heard built up gunk can really cause issues with the heat. I flushed with water - but it wasn't causing the issue...

 

Thanks for the reply. I have checked out most everything and am convinced the heater core is plugged up. To night I drove home from work with the blower off,and when I got home ,I put my hand up to the defrost vent and turned the blower on. I had warm air for about 30 sec. This backed up what I was thinking .The heater core is not flowing enough water to stay hot with the blower on. I will try to flush it this weekend.

 

I flushed the heater core today and I have heat. Air temp coming put of the vent is 156 degrees

 

I am in the same boat here. I just got back from a job for 6 months, and daughter said 2012 Jeep Liberty heater not working.
Door actuator on drivers side is fine, works and moves gears. Fan/blower adjusts speed accordingly.
Just no heat.
Water is full, no leaks, and over flow is fine. All hoses are hot when up to temperature.
Any fuses? Any thing else can cause this?