Hi...

I see there has been a lot of posts about this but I am unable to find a vacuum leak...

Is there a good way to disect where it is? I have been taking tubes apart and putting low pressure air into them to see if there is a leak....nothing so far.

Could the vacuum motor pump be bad? The 4X4 enages...both low and high.

I appreciate any help..

Hartwa

 

do you have the electronic automatic temp control or the normal manual A/C controls?

 

Just manual control...thanks

 

I checked the vacuum at the switch and there is no vacuum coming is with the key on but the engine off. When the engine is running there is vacuum on the black line. I think that there should be a vacuum with the key on engine off though... The vents used to switch without the engine running.. Thoughts anyone???

Where is the motor that genrates the vacuum on the 02 F150 SC?

Thanks for the help anyone can provide...

Hartwa..

 

There won't be any vacuum with the engine off unless there's some residual in the system, there's no vacuum pump. Pull the battery out and look carefully at the little plastic vacuum lines behind it.

 

I'm also experiencing the same problem with my 03 Screw. 5.4 L 4x4.
Only blows cold through the defrost even when set to max AC.
Mine is the electronic automatic temp control system.

Is there a write up on what to look for and which vacuum lines to replace and or trace out ?

 

https://www.f150online.com/forums/hv...buildable.html

this just solved my problem.
AWESOME write up !

 

There are some diagrams that are very helpful. I have not solved my problem YET. I have good vacuum all the way to the vacuum cyclinders but they still don't work. I find it strange that 2 would fail at the same time. The ones that are not working are the panel and the floor. That makes me think it is a vacuum problem but my truck pulls nearly the same vacuum as my brothers 04 F150.

I think I have to buy new vacuum cyclinders.

 

this is a stupid question (because I am not familiar with these trucks) but had the same issue with my Audi...

The door flap that opens and closes had foam on it. with the heat in Florida it just ate the foam off after time and then I started losing air flow. Could be the door is stuck? (if it's on a servo) type thing, or maybe if they use foam it has worn away? I know thats probably stupid but thought to add my .01