Great forum!

I know this is going to sound a little redundant to some, but I read through all the threads on an issue that could point me to an answer and didn't find anything. I have spent the last three hours trying to find a thread that matched my issue. I believe there was some that could lead me to a conclusion, but needed to be sure.

I have a 2004 F250 6.0 truck. My vent selector is stuck in the 'dash vent' position. I can't switch it to defrost, floor, or anything else. This past winter I noticed that heat would blow well but only through the dash vents. Now that summer is well underway I noticed that the AC blows through the dash vents also, but it doesn't blow very cold. I checked the freon, topped it off (didn't overfill), and still have the same issue. I checked the fuses and all are good also.

Of course, moving the selector to Max AC doesn't help either. Does this all point to the blend door motor? I hope not as the reading I have done means that this is one tough project to tackle.

Any and all help that can be provided is MUCH appreciated!

Keep up the good work!

 

I do believe all these symptoms strongly suggest its a near complete loss of vacuum to your control system. That's where I'd start.

 

If it was a vacuum loss, wouldn't the door be stuck in the defrost position? I read that Ford did this for safety reasons.

 

Yes, it would. You don't have a problem with a loss of the vacuum supply.

It's supposed to.

It wouldn't be expected to. That only selects the air inlet.

No. The only function of the blend door is control of the temperature. It doesn't affect outlet door selection.


Do you have the manual or the auto climate control?

 

I have manual climate control.

Sorry, I typed incorrectly... I meant the heat comes out the dash also. Also, and this could be because air is forced in by just driving down the road, but sitting at park the A/C works great! When driving down the road it gets hotter.

Moving the temperature control to hot definitely puts out hot air.

Thanks again, All!

 

Open the glovebox, empty all the stuff out of it, then squeeze both sides inward so that it drops down and you can see behind it.

Just to the left is a vacuum motor that has two vacuum lines to it, one blue on the side and one yellow on one end. On the end opposite the yellow hose is an actuator that is supposed to go in or out and is connected to a linkage that controls the panel-floor door inside the plenum.

With the mode switch in OFF and the vacuum pump running, both the hoses should have vacuum and the actuator should be fully retracted. Check for full retraction and that the linkage is not binding, stuck, broken, and that it appears to be operating the door (you can't actually see the door) inside the plenum. Move the mode to one of the AC or the VENT positions, and both hoses should go to "no vacuum" and the actuator should relax to the fully extended position and should move the internal door to the opposite position. Place the mode switch to the PNL/FLR position and there should be vacuum on the blue hose only and the actuator should move to the mid-position.

That will give you something specific to check. For airflow to only go to the vents, that actuator has to be staying in the position where both hoses have no vacuum.

If you get stuck or don't understand something, ask.

 

Understood. Thank you! I will certainly verify the positions and vacuum!

 

Ok. Finally got back home.

With the switch mode in the OFF position, neither the blue or yelllow line has vacuum.

Does this point to an issue with the vacuum pump?

Thanks again!

 

Did you not check to see if the pump was working first? Your initially reported symptom indicated that vacuum is present, otherwise almost all airflow will go out the defroster outlets unless something is mechanically jammed. You can check the Defrost/Panel vacuum motor separately, it's on left side of the plenum, above the gas pedal.

 

I agree. After reading all the threads on this issue and my vents weren't stuck in the defrost position, then the the vacuum must be working.

The blue and yellow lines are in one connector. With the switch in the OFF position, I should get some vacuum with both disconnected and the truck running. Right? Also, I verifed that the actuator can be moved in and out without much issue. Also, without pulling a line off (as I just did at the actuator), how can I verify the vacuum is running. I have a loud motor and am not sure how I can tell without doing what you just suggested.

I don't know what the plenum is.

 

You can use your finger tip to check for vacuum.

The plenum is the enclosure that the air moves through and includes the space for the blower heater and evaporator cores and for the movable doors.

There's a vacuum line that comes through the firewall behind the glove box that runs from the pump to the HVAC mode selector switch. Check that line for supply vacuum.

 

Is this vacuum line you speak of that comes through the firewall different than the blue and yellow lines that you had me check?

Ok. I found a black and white pair of vacuum hoses that feed into the blue and yellow. Neither have vacuum on them in any of the positions of the selector switch.

Any ideas?