My heater appears to work fine and my blower definetely works fine, but somewhere where these two have towork together, there is a miscommunication.

My jeep blows cold air until the engine gets up to around 2000 rpm. This is not a "jeeps take a long time to warm up" issue. I can be diriving it at 70mph for an hour and as soon as I come to an idle at a stoplight-cold air gets blown on me.

2000 JEEP Cherokee Classic, thermostat replaced multiple times (dont think its that.) Coolant levels obsessively checked, its not that.

ANY help/ideas/criticism would be helpful-I live in MN and it's getting cold.

 

Water pump not giving enough water pressure to heater core at idle?

 

.....or heater core somewhat plugged.

 

That's probably it right there

 

How about maybe a vacuum leak, vacuum is used to control the flappers in the dash, a rpm difference could affect there vacuum.

 

backflush the heater core with a garden hose and a bucket. Pull the hoses for the heater core off at the front of the engine. This gives you some room to work with. I have a nozzle end that fits inside both hoses. I start with the return side. Place the supply end in a bucket and turn the water on. You will be able to see any crude in water coming out. I usually go back and forth a few times.

When mine is plugged it blows 110 degree air, when its cleared out, it above 160. You wouldn't beleive the smallest piece of crude can stop the heat.

This would be a good place to start, its cheap and will tell you if the heat problem is heater core related.