A little help if you can:
I have a 99 Jeep GC Laredo and have heater issues. My heater blows cooler air on all settings except recirc and then I get cooked out of the Jeep. So I checked the blend door. OEM had bad foam but functioned as it should, but I replaced it with the better aluminum framed door with better foam. Problem still there. So then I flushed the entire system and it got better. I could drive in comfort without getting hot or cold but the air flow was still much cooler than if I had it on recirc. I have noticed that if the outside air is colder it blows cooler. Warmer the outside air is, warmer the heater is. But this morning I started the drive to work in 32°f and half way thru the commute it was 11°f and the heater was blowing 50°. So I am wondering if there is an outside air vent or intake that is overpowering the heating system and if so, is there a way to block or shield it from overcoming the heating system.

 

It shouldnt. When was the last time you changedout the heater core? They can get plugged up with crap and then not perform properly.

 

Never. As far as I know it's original. I flushed it and seemed to be getting good flow. I used the Core lines to flush and reversed, flushing in both directions

 

I have the same problem with my 2000 WJ. With mine, the blower works fine, but it doesn't seem to move much air. If you put it on recirc, it heats up the cabin real well, after a while. I'm thinking there is debris plugging the air passages in the core, stuff that got down thru the cowl vent. My plan, when I get to it, is to remove the blower motor and use my shop vac on discharge and blow air up the floor heat ducts to see if anything will blow out. I'm expecting pine needles and tree seeds.

I'd have to have the engine running or all those doors would be closed.

 

Dave, my air flow is pretty good. In fact it spits out dry rotted foam from the original blend door on occasion. and if using re-circ it gets hot really quick, just fogs the glass. That's why I am stumped

 

So on the drive last night and this morning the outside air was 10-15 degrees warmer and my heater blew much warmer air. I'm stumped. This has to be something other than a clogged core. When I flushed the core I got the same water pressure going out as I was putting in. Maybe debris blockage on the outside? But I'm not sure about that as I'm getting great flow from the air vents

 

I have noticed a lack of heat when it's very cold outside and the blower is on high. It gets warmer on lower speeds. That I assumed was due to colder air having to be warmed in less time while passing thru the core. Also, my heater does an adequate job when the air is above about 35* Not great, but adequate.

 

did you check the damper,or get it figured out

 

Blend door is new and functions fine. I'm curious if the more extreme colder temps are affecting the temperature control switch causing the blend door to remain partially open?

No. Problem has yet to be solved

 

Warm/hot air, moving at high speed, will appear to feel cooler than the same temperature are moving at a slower speed.

 

It's obviously much cooler. The vehicle cools down also

 

I get the same thing. Only my temp gauge drops from 210 at idle to 175 going up the road. I've changed the thermostat and same result. I thought about putting cardboard in front of the radiator to keep more heat in the coolant during the winter but have not tried it yet.