Sometime back, can't find thread, I posted about less air volume from dash registers when not in MAX selection.
I never finished and am back.
I have since alldata subscription. And as previously found, there should be no difference per block diagrams as to the amount of air when moving from MAX to the next selection. So what is going on?
The only change should be whether it is inside or outside air and it should change nothing else. Or is this another Fine Ford Fubar?
I have had other Ford products of similar vintage and none of them behaved this way?
Any ideas?

 

Mine sounds as if there is more air but it is just the sound of the air being ingested from the interior rather than from the outside. The volume coming out the air vents stays the same.

 

You can and often do have more air velocity out the vents in recirculate mode since the system is just moving air around inside the cabin instead of bringing in outside air and then pushing it out the cabin exhaust vents.

 

Testing was done to eliminate backpressure such as verifying with windows open. There is definitely less volume, less force at the dash registers.
There also seems to be less air in any mode other than MAX and that was shown again last night when driving home late after rain inducing high humidity. Defog/Defrost definitely seemed way below a good standard.

Thoughts that I am considering.
1) Some sort of blockage for outside air and needing to pull outside cowl for inspection. Fan motor had been pulled to watch movement of recirculate door and it was working.
2) Something is wrong in the vacuum switching system. I'm a bit befuddled with the possibilities there, that is what state could cause a flow decrease?

3)It would seem the blend door is working although I don't know how much out of calibration it might be. That is, was it put in at the factory by a blind monkey?
But it certainly is not out of whack enough to effect flow in a major way when in MAX selection. It could be off enough to impact maximum cooling on a 90 degree plus day.

Does anyone know if there is a position on any of the diverter doors such as only partially activated that would negatively impact air flow???

 

1. Worth checking. Also, check for a dealer-installed cabin air filter.

2. None, unless there is a blockage in the ductwork.

3. The blend door only affects how much air is diverted through or around the heater core. It should not affect the volume of airflow unless its clogged with dust, dirt, or critter nests, same as the evaporator core.

 

Thanks for reassurance.
No CAF.
2. The monkey comment pertained to all diverter doors. And I notice something a bit different about the floor diverter. It is two stage with two vacuum lines, but not sure that would create issue.

If block diagram is correct, it is impossible for this condition to occur because of door positioning. The air would be diverted somewhere, not restricted, except by ducting size. So a double check to make sure air is not being diverted elsewhere causing the decrease from MAX position.

Right now, and next check for sure, make sure cowl is clear so it can get plenty of outside air. Then later tear into more of dash workings and maybe look into the memory that my Dad may have had that floor diverter actuator replaced under warranty.

 

Do you have manual or digital control head?

 

Manual system

 

Either way I'd recommend checking for a vacuum leak.

The digital head is a known issue for internal vacuum leaks.

 

Pretty sure I've located the problem. See my new thread "Fake CAF". I started a new one because this issue deserves a new one. The location and nothing exists pertaining to this pseudo filter is amazing along with most who have replied seem to think that is proper operation. Plus those I've talked to face on and checked there vehicles finding the same results. This is likely a NHTSA recall because of the reduced and very bad defogging and poor defrosting that occurs because of reduced air flow. Anyone knowing of a Ford fix?