I have a 2002 F150XL.
The air only blows out the defrost (by default), not the dash or floor.
This one doesn't have the o-rings.
Where do I look next?
Thank you!

 

The vacuum defaults to defrost of there is a leak.

Blend door also causes issues.

Highly unlikely the switch is the problem.

 

Vacuum leak.

 

I just got an Error Code P0401
Exhaust gas recirculation (EGR) flow insufficient detected.

 

Now Google P0401 and look how to solve that problem.

 

Yes, it was a vacuum leak. Thank you!

(the error code was a separate issue)

 

Mine won't go to floor, it only goes to defrost. But it comes out the vent just fine.

Would this still indicate a vacuum leak?

 

If system works anywhere other than defrost vacuum should be ok. Early year trucks had a straight 90^ rod on the actuator. Some would fall off. Actuator is by the accelerator pedal. Check the actuator in floor mode. If you have vacuum pull the actuator bolts. If it just falls out, it was unhooked. Updated actuator had a slight bend at the end of the straight 90^. It was usually a pain to hook the actuator back up to the door.

 

Good info. Thank you

 

Check the vacuum canisters behind the battery box. The seams split and cause a vacuum leak. Can be repaired with rtv silicone. Also inspect the vacuum check valves in line with the hard vacuum line passenger side of the firewall. Should flow in only one direction.