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Air blend door

alexgalexg

NAXJA Forum User
Location
Connecticut
98 XJ 4.0 automatic 3.5'lift
Ever since I put this barn find on the road in 2016 I have bad poor heat. And this year it seems worse than ever. No matter how much I flush the heater core a little brown will come out but not much, and coolant flows through it freely.

My heat is very weak and I cant remember the last time I was warm in it and below freezing FORGET IT IM IN AN ICE BOX.

I have looked at a lot of threads about blend doors and it seems like it could be the problem but usually people complain about air not being diverted to certain places. I only have the issue with very weal heat, no issue with changing where air flows.

Any thoughts? Still blend door?

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I just did a heater core replacement so the blend door is fresh in my mind

Blend door has nothing to do with where the air comes out -- It simply controls how much air flows over the heater core

From what you are describing your problem could certainly be an inoperable blend door -- everything else will function fine if the blend door doesn't operate properly -- except you'll get no heat

I have a 2000 so my blend door is controlled by an electric solenoid -- Yours should be vacuum controlled -- I would imagine you could still test -- The actuator should be accessible in the passenger footwell -- At the bottom of the heater box, left side closer to the trans hump -- Might be easier to see if you pull the glove compartment

Try pulling the blend door actuator and operating the blend door by hand -- the actuator should just pull off of a shaft once unbolted -- that shaft is the bottom of the blend door -- It should rotate a quarter turn -- you will feel any bind -- should give you an idea of it's range of movement -- should rotate about 90 degrees -- you should also be able to do this manually and get heat

Hopefully this test will let you know if you have to open up the heater box -- there is no other way to access the door without actually pulling the heater box -- It's not too terrible, straight forward job but time consuming -- I did mine over a few nights -- Maybe you'll get lucky and it will be the actuator...
 
I just did a heater core replacement so the blend door is fresh in my mind

Blend door has nothing to do with where the air comes out -- It simply controls how much air flows over the heater core

From what you are describing your problem could certainly be an inoperable blend door -- everything else will function fine if the blend door doesn't operate properly -- except you'll get no heat

I have a 2000 so my blend door is controlled by an electric solenoid -- Yours should be vacuum controlled -- I would imagine you could still test -- The actuator should be accessible in the passenger footwell -- At the bottom of the heater box, left side closer to the trans hump -- Might be easier to see if you pull the glove compartment

Try pulling the blend door actuator and operating the blend door by hand -- the actuator should just pull off of a shaft once unbolted -- that shaft is the bottom of the blend door -- It should rotate a quarter turn -- you will feel any bind -- should give you an idea of it's range of movement -- should rotate about 90 degrees -- you should also be able to do this manually and get heat

Hopefully this test will let you know if you have to open up the heater box -- there is no other way to access the door without actually pulling the heater box -- It's not too terrible, straight forward job but time consuming -- I did mine over a few nights -- Maybe you'll get lucky and it will be the actuator...
Thank you so much for the detailed reply. I get very little heat but to even more suspect that door my heater control knob does not like to stay on max heat. It pops back a notch frequently. Hopefully I can get it all working without taking the entire assembly out.

I'll update as soon as I can look into it

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I forgot to mention that it may be a little hard to turn the blend door with your fingers alone — it should turn smoothly, travel about 90 degrees, but may need a little more than finger strength to turn it
 
I forgot to mention that it may be a little hard to turn the blend door with your fingers alone — it should turn smoothly, travel about 90 degrees, but may need a little more than finger strength to turn it
Once its operating as it should does the door turn freely? Neither of my jeeps have had this issue until now so I'm not sure what to expect

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Freely, yes but there is resistance -- On my 2000 the wiper door has a rubber seal, kinda like windshield wiper rubber

you also don't have much to grab at the bottom of the heater box -- the blend door shaft is short and thin -- really only getting 2 fingers on it -- makes it just hard enough to turn that you may need to use something for a little help

Honestly if it turned freely by hand I'd expect something wrong inside -- shouldn't be loose, floppy or just too easy like no resistance -- I would expect something broken then
 
Freely, yes but there is resistance -- On my 2000 the wiper door has a rubber seal, kinda like windshield wiper rubber

you also don't have much to grab at the bottom of the heater box -- the blend door shaft is short and thin -- really only getting 2 fingers on it -- makes it just hard enough to turn that you may need to use something for a little help

Honestly if it turned freely by hand I'd expect something wrong inside -- shouldn't be loose, floppy or just too easy like no resistance -- I would expect something broken then
I mean I have flushed the core like 20x in the past 2 years and it still spits out brown so I'm not going to be too heartbroken if it doesnt work out. But at that point I will probably have to go the whole winter with little heat since a heater core takes so much dash gutting to get out.

Thanks for the detailed insight

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Honestly it's not a tough job -- No reason to go the whole winter -- do it sooner rather than later if you don't have a garage to work in

It's tedious but not difficult -- I didn't pull the steering column -- just unbolted it a laid it on the front seat -- The dash actually comes off fairly easily and doesn't need to come completely out -- Leave all the wires connected and just pull the passenger side far enough to get the heater box out

Heater box comes out fairly easily too -- 5 nuts accessed from the engine compartment on studs mounted to the heater box -- remove the studs and pull the box -- be sure to clean those studs with a wire brush before even attempting to remove the nuts then a quality lube -- don't want those studs to spin in their plastic mounts

Must disconnect AC evaporator -- harbor freight has the disconnect tools for cheap -- you will loose your freon charge which you shouldn't just let out into the atmosphere

If you're going to pull the box then replace the heater core, evaporator and AC accumulator -- most likely you need a new blend door and buy the seal kit for the heater box -- saves time, you don't have to be gentle removing the seals, and you don't have to fabricate seals -- unless you're in no rush then you can make seals and save a few $$$

I have a 97 parts jeep -- I started pulling the dash as a trial run before I did my 2000 -- I was going to use the parts heater box, but realized it wasn't the same with the 2000 -- different blend door -- anyway, I'm in NJ -- if you want to drive down we can finish removing the heater box and you can see what is involved -- I'd sell you that heater box and you could rebuild it before even touching your jeep -- then you would just need to remove yours and swap in the newly rebuilt setup -- should be able to do that in 1 day

If you really wanted you could buy the heater core, evaporator, blend door and come down and we could rebuild that heater box together -- then take it home and swap it out with the new seals
 
Honestly it's not a tough job -- No reason to go the whole winter -- do it sooner rather than later if you don't have a garage to work in

It's tedious but not difficult -- I didn't pull the steering column -- just unbolted it a laid it on the front seat -- The dash actually comes off fairly easily and doesn't need to come completely out -- Leave all the wires connected and just pull the passenger side far enough to get the heater box out

Heater box comes out fairly easily too -- 5 nuts accessed from the engine compartment on studs mounted to the heater box -- remove the studs and pull the box -- be sure to clean those studs with a wire brush before even attempting to remove the nuts then a quality lube -- don't want those studs to spin in their plastic mounts

Must disconnect AC evaporator -- harbor freight has the disconnect tools for cheap -- you will loose your freon charge which you shouldn't just let out into the atmosphere

If you're going to pull the box then replace the heater core, evaporator and AC accumulator -- most likely you need a new blend door and buy the seal kit for the heater box -- saves time, you don't have to be gentle removing the seals, and you don't have to fabricate seals -- unless you're in no rush then you can make seals and save a few $$$

I have a 97 parts jeep -- I started pulling the dash as a trial run before I did my 2000 -- I was going to use the parts heater box, but realized it wasn't the same with the 2000 -- different blend door -- anyway, I'm in NJ -- if you want to drive down we can finish removing the heater box and you can see what is involved -- I'd sell you that heater box and you could rebuild it before even touching your jeep -- then you would just need to remove yours and swap in the newly rebuilt setup -- should be able to do that in 1 day

If you really wanted you could buy the heater core, evaporator, blend door and come down and we could rebuild that heater box together -- then take it home and swap it out with the new seals
NJ isnt too far from me I'm in ct. I'm finishing up a few adjustments to my new lift and then fixing this heat mess. You are very kind. I dont think I'll need help with the box itself but I will definitely let you know if I do. Thanks so much again man!

Theres a place this offroad club goes to frequently in NJ. Wharton forest or something like that? These people mostly drive modern 4x4 vehicles so even if you had a stocker you'll have no trouble keeping up with them at all. You should join in sometime in the spring

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