[stretch2187]

I went through this with my jeep. I finally tracked the problem back to the stepper motor that moves the blend door. With the motor pulled off you should be able to twist the axle that runs up to the blend door easily by hand with the air on low, if the air is on high, it is very hard twist the axle by hand but you should still be able to do it. If you have the motor pulled off and you can't twist the axle then your blend door is jammed.

[kadetklapp]

if the air is on high, it is very hard twist the axle by hand but you should still be able to do it. If you have the motor pulled off and you can't twist the axle then your blend door is jammed.

Using a stout, flat blade screwdriver, neither me, or my mechanic (and we are big guy) can turn the blend door without breaking something. It's stuck HARD and fast. Thanks for the insight. I'm glad someone else has a non-heater core problem and can help me diagnose.

[stretch2187]

I had a heater core problem too. A previous owner had bypassed the heater core because of a leak. I was able to fix the leak with stop leak but then found I didn't have heat. I was scared I had plugged the core but I discovered I had good flow through the core. After pulling my hair out for a few days I finally figured out the stepper motor was bad. I actually didn't replace the motor, it was so easy to turn the door by had I didn't worry about it.

[kadetklapp]

Yes, my motor is fine, but it can't turn the broken door. The motor almost pops out of the screws it's trying to turn the door so hard.

[210000cherokee]

Where do you find the stepper motor at. Is it down by the floor towards the center of the vehicle

[kadetklapp]

K, cut a hole in the heater box, moved the blend door by hand and





























cold ambient air.


1999 Jeep Cherokee Sport FS
$1700 cash, come get it.

[kadetklapp]

**Update**

Friend of mine and jeep afficianado/certfied mechanic has been trying to convince me to figure out what the problem is.

Friday night we performed an epic coolant flush. A thick plug of **** came slamming out of the upper port and we thought maybe that was our problem. No dice.

Then we got scientific and busted out the volt meter which has an accurate temperature sensor setting on it. We checked the input and output heater hoses at 155* give or take 6,7 degrees on both hoses. Then we got in the truck and ran the sensor lead down the vents. We found the idle temperature (in a heated shop) to be 105*F. When we drove the Jeep down the road, the temperature plummeted to 70* and then on down to 60*F. This is on a cold evening, 30* outside or so.

Since there is a huge hole in the heater box from when I accessed the blend door, my mechanic reached inside and grabbed what we think was the heater core, and burnt the crap out of his hand. Is it possible to grab the heater core from that position, or would that have been the evap core? Either way, he says it was very hot.

I was convinced by another mechanic to just try swapping in a new thermostat, and after being scalded by hot coolant (my own fault) last night I did so, and it made no difference.

[jeeptown]

Still sounds like you have no air flow through the core. If your buddy burnt his hand on the core than you have plenty of coolant getting through. Your problem is your blend door or multiple door issues. Sometimes you just got to get in there and see whats going on. I've pulled a few of these before and they are not that bad to do. Worst thing is evacuating your ac system and recharging at home. I mean really you could of had this fixed along time ago you mentioned your blend door was jammed up, Youv'e solved your problem most likely now you just need to do it.

[thundergod1320]

To flush heater core, I've found that if you remove both hoses at the block and blow them out, then slowly fill one, using a funnel, till the stuff comes out the other hose (keeping both vertical above the core) with CLR or other household rust/lime remover. leave it that way overnight, then drain and backflush with a garden hose. In 9 of ten times, it works great, and it isn't as caustic as regular flush so it dosen't eat holes in the core! If you have lots of rust in the block, that can be a real problem. Whatever you find in the heater core is likely in your radiator as well (and the radiators in these puppies aren't all that large to begin with!) I have a 91 that I've had to flush out three times since we bought it last year, and crap still keeps coming out of the block! I'll probably pull out some block plugs next spring and really get in there.

[FrankZ]

If the outside of the heatercore or the evaporator is plaugged with dirt your airflow will be greatly reduced.

FWIW,
This is how I spent last weekend...

[AZ Jeff]

Originally Posted by kadetklapp

**Update**..........
Since there is a huge hole in the heater box from when I accessed the blend door, my mechanic reached inside and grabbed what we think was the heater core, and burnt the crap out of his hand. Is it possible to grab the heater core from that position, or would that have been the evap core? Either way, he says it was very hot.

Based on that info, I say your heater core is plugged up with a bunch of dirt, crap, leaves, etc., like FrankZ suggests. Take it out and clean it off.

Sorry, but that means the same R&R procedure that is used to replace said same core.......

[xjfever]

If you remove it to clean it, go ahead and replace the core. They aren't that expensive, and you dont want to do this twice.

[filluptrk]

I looked at that heater treater, it seems pretty cleverly engineered. Might be an inexpensive way to fix the problem permanently. Phil

[kadetklapp]

If you remove it to clean it, go ahead and replace the core. They aren't that expensive, and you dont want to do this twice

Agreed. Right now its not if, but when. I guess I am fortunate that I have access to a warm shop and a good Jeep friend who is an ASE mechanic. I'm just really PO'd about having to evacuate the AC and pulling the airbags. Two things I try not to mess with when working on my vehicles.

Plus, it's the holidays, money is tight, and time is of the essence. The roads get crappy here and my XJ is a champ at these road conditions, but the "being cold" part puts a damper on what should be a positive Jeep experiance....

[Ed Rico]

There's no workaround for discharging the A/C as the evaporator comes with the HVAC box when you remove it from the cabin. If it's any consolation, the steering column and dash don't have to come out completely (there's room to pull the HVAC box out from below the passenger side of the dash if you lift the dash up and just let the column droop with steering wheel against the seat), so there's no worry about the airbags as long as you have the battery disconnected during the removal & install.

-Ed Rico