1989 ford f150

ac is blowing out of defrost only??

Thanks

 

Suggest the most likely suspect is a vacuum leak somewhere in the HVAC tubing assemblies.

Typical suspect on our model years is the white vacuum line going to the recirculation damper in the engine compartment on the passenger side of the firewall. Basically disintegrates with age. This will generally result in the A/C shifting to the defroster under acceleration or heavier load while on Max A/C.

Assuming that it is blowing out of the defrost all the time - suggest to inspect the vacuum line to the HVAC cluster coming from the air intake plenum. This line is black and is located in a cluster connection of vacuum lines. Look for the one that goes through the firewall.

Lower on the list of probabilities are problems with the HVAC selector assembly, problem with the vacuum line to the floor / defrost damper, the stuck blending door, or a failed vacuum actuator.

 

Check your vacuum hoses, especially the white one that runs from the engine compartment into the area behind the glove compartment.

 

Thanks all

Will check the lines..

 

I had noticed a while ago that my white line was disintegrated as mentioned. Is there a fix for this? I taped it up for now. But, I'd like to replace that line all together. However it is glued together with a couple of other thicker lines going through the firewall.

I also hear a lot of vacuum leaking in the cab when the ventilation is off.