Hi Guys (and gals).. I just hit 150,000 miles in my '98 F-150 this last week, and had basically my first non-maintenance issue pop up over the weekend. I am no longer able to control the termperature of my HVAC controls. When I have the vent or AC on, when it is blowing cold air with the temperature control on cold, when I move the temperature gauge to the red area for hot air, the termperature of the air stays the same (cold.) It was doing the opposite earlier today (where it was blowing hot air, and when moving the termperature gauge back to cold, the temperature remained hot.) Unfortunately it is back stuck on cold air again now (which I wish i knew how to get back to warm air with it being Winter.) The issue just began yesterday. In searching thru this forum, it appears the 'blend door' may possibly be my issue. Has anyone else had the same issue that can point me in the right direction, or can anyone confirm that the blend door is my problem? Any ideas on how to get back to warm air between now and the time I get it figured out?

Thanks in advance!

 

STX/98,
You are describing the same problem I had a short while back. I found my blend door to be broken. I verified this by removing the blend door actuator motor located underneath the dash on the transmission tunnel. I replaced the blend door and the heater core while I was there. Doing this requires partial (my choice) or complete removal of the dash. It wasn't really difficult, just very time consuming. I spent an entire Saturday working with my son to make the repair. In my opinion it was worth it. I spent around $100 on parts and I've heard that the Ford house will charge in the neighborhood of $800 to $1100 based on what others have posted. There is a very good pictoral posted by Quintin in this same forum that you should take a look at to help you decide if you want to tackle the job. I also have some very detailed instructions I received from another forum member that I could email to you if you'd like. Hope this info helps.

Alan

 

I had a similar issue to this as have many other people on this site. Check your blend ****. It just pulls off. Many people (myself included) have had the back side of the **** crack ever so slightly that when you turn the **** it doesn't actually turn the shaft it's connected too. It just kind of freewheels I guess. I got a new **** at the dealership for around $4.00.

If your blend door was broken I would think that you wouldn't be able to get heat sometimes and AC at others. It would be stuck on one or the other and it would never change. My dad's 90 F250 had the blend cable (back when it was a cable and a lever) break one time. It was stuck where it was. I'm pretty confident if the blend door breaks or quits working it stays at its last setting.

When my **** was broken I would push against the **** like I was pushing into the dash and then turn it. This would create enough force/friction to turn the little shaft. To test it for sure you could try taking the **** off and turning the little shaft it controls by hand or with a pair of pliers. Once the engine has warmed up you will be able to tell instantly if it can still switch between hot and cold. Just be gentle enough not to break it off or you will have bigger problems!

 

Alan,

If you could forward those detailed instructions over, I sure would appreciate it. My email address is [removed] . I am a little hesitant to take the dash off, as I still remember some pictures posted here a year or more ago with the dash off during a heater core swap that looked a little intimidating to say the least. I will search for the thread you mentioned by Quintin to take another look at what exactly is involved in removing the dash. I'm assuming once the dash is out of the way, it a relatively easy swap? Also, when your blender door broke, was the HVAC system stuck (permanently) blowing either hot or cold air? It would seem like if it broke, it would stay where it was at last, and would not ever change like I have expierenced?

Thanks for the help!

 

I had thought the same thing.. It seems to be swapping back and forth (with no change in the termperature control) between either cold or hot air at the time I start the truck up. Usually when I first start the truck up is when I notice any change between hot and cold air if it is going to change, and it stays the same untell it swaps again at someone point when it is started again. (When I say started, I mean the ignititon to the truck, not just the vent.) I tried pushing in the temperature control as you mentioned thinking it was possibly just an issue with the **** itself, but that did not seem to make any difference. I will check the **** out again as you mentioned by pulling it off and verifying it does the same thing with a pair of pliers. Assuming the **** is not the issue, with the temperature of the air not permanently stuck on either hot or cold, is there anything else I should consider besides the blender door? Any way to troubleshoot it without removing the dash first? I sure appreciate the help.. (This would be a crummy way to spend a grand if this is that expensive of a repair!)

 

STX/98,
I’ve sent the instructions to your email account but another source of your problem could be the actuator motor. When you turn the temp control **** it activates an electronic actuator motor that is located under the dash on the transmission tunnel. The actuator is directly connected to the blend door that is located in the plenum, which is buried in the dash. To access the motor requires removal of the black plastic cover piece and a few other pieces. Here's a link that describes the procedure in detail, https://www.f150online.com/forums/sh...d.php?t=212548 . I did this first when my blend door started acting up and it allowed me to verify that the actuator was working correctly. Once I had it removed I just turned the key to the On position and moved the temp control **** from hot to cold and saw the actuator move accordingly.
Also when you have the actuator out you can take a mirror and look up into the dash where the actuator shaft goes. The shaft goes directly into the hinge portion of the blend door. When I did this I could clearly see that the blend door was cracked. I tried to position the door in the hot position manually but it never got better than luke warm. This convinced me to go ahead and fix it. Also, when my blend door initially broke it was weird because the temperature would be cold for a while then switch to hot without me changing the temp setting, just like yours. It did this for a week or so then finally got stuck in the cold position. I’m not sure how to explain this but it happened to me and I have read in this forum that it has happened to others as well.
Here’s the link to Quintin’s write up on removing the dash that I mentioned. https://www.f150online.com/forums/sh...d.php?t=216009 . The eighth and ninth pictures show the blend door in position and the broken hinge section. I didn’t think removing the dash was too difficult and it certainly saved me a lot of money. I like to think I’m somewhat mechanically inclined but I’m no mechanic thats for sure but with the help of my son we got this done in a day no problem. We just took our time and used zip lock bags and tape labels to organize the bits and pieces we removed and marked then with the corresponding step number in the instructions. As for this repair costing $1000 I just picked that up by reading other posts. I would suggest getting a quote from your dealer before you decide what to do. When I bought the new door at my dealer I casually asked the service manager what it would cost and he said, “man that would be expensive because the dash has to be removed”. This was enough to convince me that I could install a $35 part cheaper and probably better than Ford. By the way, my dash has so squeaks, rattles, or groans after all of this. Hope this helps you get the heat back on…

Alan

 

Alan,

I can't tell you how much appreciate all of your help. I got your email this afternoon, and after taking a look at it I plan on trying to do it myself sometime around the first of the year. (I did check with my mechanic, and was quoted around $700 to $800 if they had to remove the dash. He mentioned he's had about 6 F-150's over the last few years with the same issue, and only 3 of them needed the blender door replaced. The other two had some other type of other minor issues with either the accutator or the wiring.) I'm at 150,000 miles, so I will replace the heater core while I am at it. Anything else I should take a look at while the dash is off while the oppurtunity is available?

 

STX/98,
I know how you feel. I felt the same when I got them myself, and really felt good when I was finished and it Worked! Hummm, other things to do. At 150,000 I'd sure drain and flush the cooling system, clean the inside of the plenum to kill any odor causing bacteria, replace weatherstrip in the plenum that looks bad (you'll need some for the heater core anyway) and check the tightness of every fastener you can find that is covered up with the dash. You don't want to have an squeaks when you're done.

Good luck and Merry Christmas...Alan

 

Just wanted to report back that I finally swapped out my heater core and blender door over the weekend, and at long-last I've got heat!!! The swap took a while (10-15 hours) although I got it back together with no rattles or squeaks whatsoever. I'm sure if I had it to do over again, I could do it in about half the time now that I have a better idea of what I'm doing. Thanks again for your help AlanT - the directions you sent over were priceless.

 

good info this helps

 

I did a search on the forum for this problem. After reading several posts, I checked the blend door motor thinking it might be that. But that was ok. One heater hose is warm and the other one is not warm. Could it be a valve that is not working? Or the thermostat?

 

You don't have any coolant flow through the heater core. Usually, this is due to a clogged core.

No valve in that coolant loop unless it was added by a previous owner on their own.

 

same problem with mine, it just blows cold air no matter what. and i can hear the blend door operating so i know its not that

 

I'm having a weird problem with my truck that started happening last winter. While driving and running the HVAC on one of the vent settings of Vent or Floor (I have the automatic control) and the temp at 90*, I will suddenly loose heat after it running for a bit. If I switch to one of the settings that uses the Compressor (Max, Automatic, Panel/Floor, Def, Def/Floor) I have my heat back but not on the vent settings.

Turning off the HVAC makes no change and I can switch through all the settings and if the compressor is on I have heat, but on the vent and floor settings I don't. Once I turn the truck off and restart it I have heat again and usually don't have an issue for a while. The problem is intermittent and I can't reproduce it with any consistency, it will just happen while driving. I'm pretty sure it is not a blend door issue since I have heat with the compressor running. I'm thinking the problem lies with the automatic climate control unit.


Any ideas?

 

Hi,


A new member here with a 1998 F150 that has the infamous broken blend door. I had the problem with the blender door being broken. I replaced the door and then i took the motor and opened it up because when you turn between hot/cold the motor would not turn. So i took it out and opened it like you and directly hooked it up to a 12v battery and voila it works. So im stuck. My motor isnt broken and opened up the **** and their isnt anything to fix inthere either. So why isnt the motor turning on? Oh i also checked all the fuses and didnt find a single burnt one. any advice?