Jeep TJ defrost not blowing air

[JammedJeep]

I tried to use the defrost and the blower motor doesn't work only on both defrost and defrost + floor settings. All other settings work fine. I can feel the air moving through a little when I'm moving so its not blocked. I suspect the setting switch is broken or dirty. Any ideas?

 

[LJBean]

You may have a vacuum leak since the airflow doors are operated with vacuum actuators. When I had a similar issue, I found that a vacuum line had separated in the engine bay where it went through the firewall just above where the heater hoses connect to the heater core lines. I repaired the vacuum line and that fixed it for me.

 

[Rancho LJ]

This is a photo from the driver side footwell looking towards center. The blue and yellow vacuum lines lead to the defrost actuator. Make sure they're still attached. The lines run across the HVAC box towards the passenger side where they will be visible from behind the glove box. The actuator vacuum lines connect to the white plug that's to the lower right of the fuse panel behind the glove box.

 

[TheBoogieman]

You may have a vacuum leak since the airflow doors are operated with vacuum actuators. When I had a similar issue, I found that a vacuum line had separated in the engine bay where it went through the firewall just above where the heater hoses connect to the heater core lines. I repaired the vacuum line and that fixed it for me.

I had a couple of Jeeps do the same thing.

 

[KennethS]

My experience has been a vacuum leak results in air blowing out the floor heater vents only. The OP said there’s no fan on HEAT and DEFROST but all the other settings work fine.

 

[JammedJeep]

It's not a vacuum leak its just the fan that actually pushes the air doesn't work ONLY on both defrost settings. When I'm moving i can feel air come through so it is NOT BLOCKED. Is this a feature or a bug because I can't find anything online about it.