Blend Door Problem, or Something else? | Ford Explorer Forums - Serious Explorations

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Blend Door Problem, or Something else?


Well-Known Member
June 13, 2003
Reaction score
City, State
Wilm., DE
Year, Model & Trim Level
99 XL

I have been reading many of these messages and a link to a site regarding the notorious blend door fix since I am trying to determine just what my problem with my 1999 XL 4x4 might be (72,000mi). I have read through the Haynes Repair Manual too. I have had so many problems with this vehicle and have but only logged 2000 miles since last Sept. when I bought it. Seems like most of the miles come from going to repair appts, or parts stores. Most of the repairs were necessary, however, not because of design flaws but becausse the previous leasee was hard on the poor thing. $3000 later, and now a potential problem with the climate system.

I have gathered from several messages (and reviewed some pics) that if it is bad both the plenum and blend door need replacing in a battle that takes a few days and using a lot of anger management techniques. But from what I can summarize, only model yrs 1995-1999, and manufactured before 4/98 are likely to have units that fail? And when/if the unit does fail the system only gives either cold or hot?

Mine was manuf in 6/99, does not have auto climate control. My problem is that when running the A/C Max I do not believe that the cab is shut off from the outside air as it should be. I can strongly smell diesel fumes while the A/C Max is running (and behind a truck), or smell the county landfill when passing by. I know that this would not occurr in my old 1984 Ford LTD using the same settings. I am under the impression, like with my old Ford LTD, when running A/C Max the system recirculates the cabin air rather than drawing in outside air. Since I have severe allergies coupled with asthma it's very important that I can control my inside air. I now this cannot be done with the heater, so I do not use the heater hardly at all, even while living in WY and Montana. I drive dirt roads quite a bit when going to remote trailheads for backpacking so again, not having the ability to shut out dirt and pollen....could trigger an asthma attack.

If anyone that was able to read through my rambling and has any suggestions, I'd really appreciate it. I return to WY and MT, leaving by the end of June


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Try lowering you glove box and releasing the side tabs to completely lower the glove box. So that you can actually see the blend door. You should see it in action as you go from max a/c to normal. In max you should see the blend door go up and expose the inside air to the air box and at the same time close off the outside air. Let me know what you see.

so are you saying that all your settings work, hot and cold? but your getting a bad smell from the max a/c. if this is the case i would have a hard time seeing that it was the blend door. like you said before, all previous blend door cases have involved one or the other(hot/cold) being cut off due to the door breaking. good luck and let us know. trust me i've been there, to the tune of $597 and that was a deal.

p.s. don't go to ford to fix, they will rape you and your family. i wen't to a electrical specialsist or really any well reputable mechanic that you know who could cut you a break.

"blend door syndrome"

Boy, that's fast help, thanks slow-demon. Your suggestion sounds logical, I'll give it a try later this eve before or after going to get groceries.

And alphabets13, thanks too. I read your ongoing posts last night and could see that my symtoms were not typical of the "blend door syndrome". But from what I remember, to answer your question, the heat worked vey well when directed either at the windshield or down to the feet (I do not use heat very much, don't like it). But somehow the outside is getting in during A/C Max when I do not want it too. I have checked all the door seals and so forth. And no, due to my first experience with the local dealer I would not trust taking my vehicle there again for repairs. (I'll gladly pay for top notch work, but they told me they had checked something I'd requested them to look at and found out there was no way they could have looked at it)

And there is a vacuum motor control visible under the passenger side's dash. I don't really know what it controls on the climate system nor how to check its function, but I don't like messing around under the dash due to the air bag sensors.

Checking the Blend Door


That's a quick way to empty the glove compartment, just like a dump truck .

The suspense of that blending door being broken finally was too much. After following slow-demon's instructions I could see that the door moves uninhibited through out its full intended range of motion; the linkages and connectors all look new and undamaged and show no signs of sticking or binding.

As best I could see and determine the foam seal atop of the door was all intact and in very good condition. This is the seal that should make contact, when the door is in the up position while in the A/C Max setting, with the outside air intake seat.

This rules out my greatest fears, and I am greatful. The invading air must come inside from some other point, and finding that point will be futile I am afraid. I think when I drive near a cattle feed lot I'll make sure to have my scuba gear near the front seat////



(Bubble Boy)

It sounds like you're blend door is OK (for now . . .), but that's not the door to the right of the glove box. The blend door is inside the heater plenum directly behind the glove box - can't see it without cutting a hole in the wall. The door to the right is just for max A/C as you stated.

I don't know that you can keep outside air getting to the car, even with max a/c. There are always vents or leaks in the body to solve pressure problems, like trying to slam a car door shut on an airtight compartment - will bounce back if you don't push hard enough and hurts your ears if you're inside. But then that doesn't explain the difference in the LTD and the X.

Good luck,

Wrong Door...embarassed

MechWolf/// Sounds like you read my article in detail. And now I kinda wished I had not donated the old LTD last month.

Thanks for the identification...the door I looked at with great satisfaction must have been the outside/recirc air door? The blend door must be invisible from any outside of the chamber view. It must be controlled by a cam lever of some sort and cable linkage.

But yes, I am certain I get unwanted air inside the cabin. This was apparent after dropping the thing off at Cottman for front differential work and a rebuild of the transfer case during a warm spell this late March. It was up to 68F so the landfill I passed was getting ripe and the odor sure was inside the Xplor while I ran the A/C Max. After dropping the vehicle off, I returned the same route in a 92 Sable while running the Max A/C and didn't smell the garbage. I rolled down the window a bit, and the wind hadn't changed direction; the rank smell was thick as a CO feed lot in July.

Well, I'll probably go look around at the plenum again and try to visualize the blend door's situation for my own education. If I keep the x for awhile longer, and the blend door obviously goes....I'll probably do the work, but hopefully when the temps get more comfortable for workin, like upper 30's mixed with a few squalls.

Thanks again, I'll be packing some 3M masks for my dirt road driving/camping/backpacking in WY & NW MT in a few weeks


2med, when you switch from A/C to Max, you should hear a very audible change in the sound of the fan. It should actually get louder inside your Ex (the whoosh of the air being sucked in from inside the cab). That's another way of knowing if the vent door is working.

You may want to look around inside and out at your firewall and make sure youare not missing any rubber plugs/etc where hoses/wires pass from the engine bay to the interior.

RE: Firewall Inspection


Good suggestions, thanks/

I just spent about an hour or so looking around for potential outside air entry points on the firewall and evap. case. I found some of the screws needed some tightening on the evap case to firewall, the blower fan to its seat, and various other screws/nuts that penetrated the firewall.

I noticed too that the tubing entering the evap case, top and bottom, might have some pinched foam allowing ouside air to enter. I'll push in some new foam as soon as I can locate some at Lowes. I think this is the major difference betwn my old LTD and this X; the evaporator in this vehicle is located in its own case inside the engine compartment. That's actually good, I think, so if a hearter core replacement is needed for example the evap doesn't need to be separated, thus saving the opening of the the A/C system lines.

I found one questionable item protruding from the lower portion of the left side firewall (as facing the firewall with hood open). It is a 9/16th OD pipe, or steel tube, that sticks out past the firewall approx an inch. It is located in line 2" below the last of the two bolts of the evap case's right side. It doesn't have paint on its circumference leading me to believe a hose was attached at one time. The pipe has gasketing on the cabin side of the firewall. Could this be a drain pipe for the evap? If so, it should probably have a 90degree- bend heater hose attached to the end so any forced air is not driven into the A/C plenum (a guess).

Think I am on to something. The air intrusion as I remember is only when I turn on the A/C Max. I do not emember having unwanted ouside air entering the cabin until I turn on the AC Max(from nothing at all on to AC Max) So either the vent door (A/C Max or recirc door I am refering to) doesn't seat properly, maybe due to the seat itself rather than the door. Or, the evap case located in the engine compartment is leaking in engine compartment air when the fan is engaged. Passing a road construction site, for example, where some diesel equip was running and the AC Max was running the diesel odor was almost immediate, like it was being piped into the cab.

Pulling the cowling off on the side of that vent door, just under the windshield wiper might give a view of the top of the recirc door's seat? Or the actual port might be located somewhere else between the fender that sophisticated ducting connects it to/

Thanks again for your direction/


If I get a chance, i'll look at mine and try and determine which tube that is and where it goes. Just curious if you could hear the change in sound I mentioned. Also, with MAX A/C running, turn temp selector all the way to hot. Let me know if the air goes from cold to hot or not.

drain tube

Thanks Tom,

I found that piece of tubing sticking out of the firewall listed in the Haynes book.The reference tells the owner of the venicle to make sure the tubing/pipe is clear for discharging evaporator condesation. The book does not show a hose attached to the pipe.

I'll try out what you suggested later on this eve while I run some errands. I am pretty sure the major difference btwn the Explr and my old LTD and the 92 Sable, where the outside air intrusion does not seem to be a problem under a/c max conditions btwn the latter 2 vehicles, is that the X places the evap and blower unit outside of the cab. That fan mounting surface might not have a proper seal, so I cut strips of open celled foam approx 1/4"x 3/8" into lengths and fit those pcs in between the mount screws and forced a better seal all around. Maybe it needed it and maybe it didn't but I did not at this point feel like taking time to pull the fan out.

twomedicine/ Bob

A lot of good info posted so far on the blend door and the recerc door.

If you wanted to it wouldn't be hard to put a switch on your recerc door to control outside air in all positions. All you would need to do is controll the vac to the recerc motor.



I tried that sequence and found the following:

1) A/C to A/C Max : sounded different with a schwissssch or a paaschisssch noise after switching. And the air velocity and volume increased with the switching. Noticable without instruments.

2) Heating in the A/C Max position: Luke-cold air in the hottest dialed setting. As the dial was rotated towards the colder settings the temp followed the trend also. Sounds like the blending is occuring.

Good tests/ Everything must be working unless you see differently.

thanks a good bit// I might be getting some air through the driver's side door seal as I can hear road noise and air movement, but the door seals are in great shape and moreover, the striker adjustment is right. Oh well, I'll see what happens. Oh-yeah...where is that website that handles Ford parts? The one that has the IAC
for $70? That would be a good resource for future reference, if you care to disclose

RiverRat, thanks for your info, sounds like a good plan. I think I remember one fellow that mentioned he disconnects and plugs the heater vacuum switch vacuum line with a golf tee to obtain a closed recirc door for heater season. I think that was a blend door thread post reply to someone like myself that doesn't want outside air pumped into their quarters.

I like the switch idea and will mull that one over and maybe take action on it in the fall. Kind of like having a similar option as the old (maybe new too) Jap cars offered; there was a little linkage switch located in the climate control panel where by a choice could be made btwn having outside air or recirc air in any setting simply by throwing it left or right. These Explr's are really quite complicated regarding all the controls. Hopefully they'll hold up while 70miles out and off the hard top.


Ford Parts Network - Banner is at the top of this page - is one. Torrie there has been very helpful with the members here. They are a sponsor here. Another is

As long as it's only getting lukewarm in Max, should be OK, especially if it gets colder after a while. The heater control valve (or the vacuum to it) may not be quite right if it stays warm as it should stop coolant from flowing to the heater core in Max.


/Thanks Tom, yes I believe the air temp was blowing warm at first and then became cooler over a time period of maybe 20 seconds after when using the A/C Max while the heat setting was at its max. That heater hose valve/switch must be doing something. I do know what that looks like so if it starts acting up it's an easy replacement.

Those sites look good. I had a bit of a problem with the search engine's ability to find the IAC for example.

Looks like by Monday that A/C Max is going to get a work-out...upper 80's- 90F


You have to search around a bit on the parts sites. IAC is actually referred to as Idle Speed Control motor or something like that... I usually just surf through the section I think it would fall under (fuel delivery for IAC if I remember correctly).

Idle Speed Control

Tom, yes, I did come across that "Idle Speed Control " while looking in the sub-categories as you suggested, and judging from the price, that must be one in the same as the IAC. Next time I'll know. It's hard to believe a dealer can look a guy in the eye and charge $190 for replacing one of those things, a job easier than changing a ceiling light bulb at home.

Looks like a very good resource, and now seeing that a new transfer case costs less than having my existing one re-built, as I did 3 mos ago, I would go new the next time since the unit could be swapped out easily, solo.

thanks again,