The a/c on my 97 w/ 5.4L does something very strange. It works fine on Max AC when driving around town or idling. When I put it under a heavier load (going up a long hill) it will divert the air blowing out of the vents at your face to the floor. The a/c is still on but it diverts the airflow to the floor. Once I lift off of the gas it will divert back and blow back to my face. What in the world could this be? Could this be a vacuum leak or ?. It is very strange. Thanks.

 

its a ford thing the a/c clutch stops because the engine is under load so not to blow hot air at you it also diverts the airflow. its perfectly fine dont worry.

 

My truck has always done it, I believe it's because the blender that controls direction ( Defrost, panel, floor, etc.) is powered by vacuum. So when your engine is under load, there is no vacuum and it defaults to defrost. This is one thing that has bugged me about my truck for years, but aside from installing a vacuum pump or upgrading to a electric solenoid (don't know if it even exists) there's not a whole lot you can do.

 

Not at all. These specific year's trucks are not designed to do any such thing. Other models to have a PCM-controlled relay, but not the 97, at least.

The 97 does not have a WOT cutout. If your clutch is dropping out, it needs repair.

Likewise, if the airflow diverts to the defroster, you have a vacuum leak or a faulty check valve. It's as simple as that.

Steve

 

X2. Cutoff maybe, but it should never switch where it is putting out the air. That tells me you have a vacuum leak.

 

My dad's 94 does this but alot more frequently so in his case, it most likely is a leak somewhere. Max A/C is primarily used as economical a/c so maybe that's why it does it. Betcha it will act different with regular a/c.

 

The compressor never kicks off. The airflow is diverted to the floor when going up a hill or under load for a longer time. The a/c is still on but blows cold air at your feet. I am thinking vacuum also. I need to locate the vacuum canister for the hvac and the check valve. Thanks Again guys. Great work.

 

Normally when this happens it is the electro vacuum swith in the dash.
However the 97 vacuum hose routing from the vacuum resovoir has some chafe points that end up putting a hole in the vacuum line. So check the entire length of vauum lines under the hood from, cracks, holes, breaks etc. If the lines are good it is probablly the switch in the dash