so i’ve had the problem where my a/c would go to defrost when accelerating didn’t entirely minded it since it still cooled me off but now it stopped changing direction entirely so it’s stuck on the defrost vents though i can still activate my a/c and when i went to look at the actuator under the hood i took the vacuum hose off and felt no vacuum or heard any and it would just stay on defrost and idea on how i should fix this it’s hot as hell and wanna fix this asap

 

IIRC, defrost is a 'default' position.

Suggest there's a vacuum leak somewhere, from coming off the source vacuum line from the manifold to the HVAC control unit, the lines to the various damper actuators, an actuator, or the control unit itself. Actuator itself may have a problem with sticking or other.

Actuator under the hood should only be under vacuum when in Max A/C mode, would look first at the vacuum line going to the actuator where you want the airflow to go, presumably the Vent. Both the Vent and the Floor actuators are up under the dash - memory fades but may be able to get a look at one of them by pulling the glove box out, at least a better view of the air plenum.

Given the rather small lines, a vacuum leak likely won't affect engine idle speed, at least not by much. Depending on how quiet the surroundings, may be able to hear it...???

 

so you rekon i should pull out the glove box and look for lines there of listen for a leak from there?

 

Pulling the glove box is pretty easy, pop the restraint cable and push the tabs, comes right out. Gives a better view from that side on what you're working with.

Bigger picture is to find the two actuators and start fiddling around - do they exercise manually freely, is vacuum there, etc. and work from there to narrow down the problem.

Could be a leak or could be a pen left on the dash that fell through the defrost vent and worked its way down over time to bind something up - just gots to work the problem.

 

Yes, defrost is the default in case of a vacuum loss
Check the vacuum canister
Either that or the one way valve has a leak IMO
Both are under the hood

 

i assume the canister is the “coffee can” but not 100% sure where the one way valve? i’ve seen a video of someone redoing their whole vac system and they showed one right above the heater core/ac would it be in the same area

 

so i assume i found my problem and went to look at the valve thing i thought y’all were talking about and moved the line and it snapped right off i’ll send a picture of the line that snapped off but what size hose you think id need to repair this one tried taking a video to post but it was too big


going into the loom

after the valve

 

5/32" ?

 

https://www.f150forum.com/f10/vacuum...112858/index2/

scroll down to post #16

 

Use washer tubing to repair the plastic lines
The vacuum line you are after goes into the cab near the AC hoses and heater core hoses
Generally, goes right into the cab from the plenum
That vacuum line after it comes out of the cab will tee at the one way valve
It tees to manifold vacuum and the coffee can or plastic reservoir (depending on year)