Blend Door Question

On a 98' model if there is an issue with the blend door will it effect cooling (a.c.) as well as heating ?
My heat output is low but my a.c. is a freezer year round.

I am currently flushing the core, it does seem to flow good but if it is scaled I know it won't transfer heat well.

I'm in exactly the same boat with my 98 so I'm curious for myself. AC works great, but the heater is weak, and ends up blowing lukewarm at best on a cold day. I flushed my core with the hose and saw no improvement, should have tried some CLR. I suspect I do have a small vacuum leak, but I don't think it is the blend door because I can change from Hot to Cold and do notice a difference.

I gave it a hose flush to start and am now flushing with diluted CLR. Doing a circulating flush via a bucket and an old boat bilge pump I had laying around.
Letting it circulate for 5-10 minutes then off to soak for an hour or more then repeat.

I had just hose flushed it a couple times over the years and seem to remember it working better than it is now.

dktool said:

I gave it a hose flush to start and am now flushing with diluted CLR. Doing a circulating flush via a bucket and an old boat bilge pump I had laying around.
Letting it circulate for 5-10 minutes then off to soak for an hour or more then repeat.

I had just hose flushed it a couple times over the years and seem to remember it working better than it is now.

Click to expand...

Can you update with how this works out? I'm having a similar issue where the heat is just "ok" on a cold day. The heat gets better with higher RPMs (more flow in the heater core?) But definitely not as hot as I've known jeeps to get (had another XJ and an LJ for a while).

Did a couple more flush cycles and have now reversed the flow for a few more then will do a clear water flush, reconnect and test.

Will post results.

I finished the flush and reconnected, haven't done a drive test yet.

For anyone with direct experience with the bland door in this model my question remains............ can it affect the heat side without affecting the cool side ?

Not really, it's the major function.

I posted-up recently:

https://www.naxja.org/forum/showthread.php?t=1152004


Try removing the motor-drive housing, under the heater box, just left of the driveshaft tunnel. Test the unit for function, once removed. It moves slowly, 90-degrees throw, or a bit less.
While off, grab the shaft, perhaps with pliers, carefully, to test for free-movement of the blend door shaft.

Even IF you do get some hot-to-cold change, it may well still be the blend door, just not moving enough... Depending on the failure picture, one could find same-level heat or cold, or more of one, and less-to-none of the other.


Quite the novelty....having chocolate-melting heat, from a few feet away from the output....after two years of little-to-no heat...

Now....just waitin' for the ice 'n snow, to deploy the new weapon.....

Follow up report;


Final got a chance to drive my pile, overall the heat output may be somewhat better but not of the "chocolate melting" quality.


I knew I already had good flow through the core so I wasn't expecting much change unless it was highly scaled and the CLR removed it.........not so much.
I may go after checking the blend door for full range of motion and sealing someday but for now it works good enough to make it though yet another brutal SoCal winter.