Hey guys my heater/ac fan is stuck in defrost but sometimes it will just kick in and start working for a couple mins before switching back to defrost. I have electronic 4wd and the odd time when I kick it into 4x4 the fan switches over from defrost. Of course it depends where I have the setting but usualy I have it in dash and floor. Any help would be great. Im thinking its a vacume line but then why would it work the odd time. Bad connection?

 

Vacuum leak somewhere for the 4x4 hubs.

When you have the heater or a/c on and you turn it to auto 4x4, it switches to defrost right?

Could be the seals on the hubs, could be the vacuum line going to the hubs or could be the vacuum pump on the inner fender passenger side under the hood. Search for it, there's info out there on this, mine is doing the same thing.

 

Most likely hubs, mine same way right now and I know my drivers side hub is toast, vacum pulls the hubs in and when you turn the switch for 4x4 and it goes to defrost that means they are leaking, Napa has them for couple dollars, think it includes O rings and new snap ring, that is seals of course, the 4x4 hubs are alot more

 

Well mine is always stuck in defrost and only the odd time when I put it in 4x4 will it switch out of defrost. My 4x4 works good so I dont know if its a leak for sure or not.

 

I'm not too familiar with the HVAC operations unfortunately. I just know when they go to defrost there is usually a vacuum leak somewhere.

My truck has two brand new hubs and still does this, so I know the lines are leaking somewhere.

 

My truck dont have the problem with the defrost. But it did with all the others and the blower speed. I had to take the dash apart and found that the back of the selector switches get worn out fairly fast. I could only use the HIGH setting for the blower and it would work at random selctions for heater or AC. Replaced the switches and they work fine now. BUt the blower selection switch is already going out again. Just a crappy part Ford makes for the truck.