The AC is blowing out the defroster instead of the vents. It has done this in the past when the vacum line to the front hub engagment was torn by brush. However, I have replaced both front hub vacum lines and still am haviung the problem. I also checked the vacum line the heater core coolant shut off from the AC mod I did a few years back. Any ideas?

 

I went thru this last week, I ended up bypassing the pvhs since I no longer have factory hubs.

 

You still running the factory autolock hubs?

 

Are the pvhs the vacum lines going to the hubs? How did you bypass them? Yes I'm still running the factory suto lock hubs

 

https://www.ford-trucks.com/forums/s...1169919&page=2

 

Go to page 2 of this forum and you will see a pic of how to bypass the pvhs( pulse vacuum hub solenoid) which is on passenger fender behind battery. It will hebrew a red and black vacuum line going into it

 

Yes the pvhs will operate your hubs in autolock

 

Check your knuckle seals.

My truck does the same thing from time to time and judging from the condition of my knuckle seals I'm fairly certain they are the cause of my problem.

 

I don't see "knuckle seals" listed in the parts list. what and where are they

 

The knuckle seal is the big O-ring that the axle goes through on the backside of the knuckle. The knuckle itself is what the upper and lower ball joints are mounted onto.

Not the best explaintion I know and yours may not be the source of your problem either, but it's worth sliding under the truck with a flashlight and taking a look at them.

Don't worry there's folks on here with a ton of knowledge that will be chiming in soon enough to help you out.

 

Back up, slow down, and we'll walk through this.

You still have your autolock hubs (as do I) and you have options here. There are those who want to lock the hubs manually and they usually buy Warn hubs. Then there are those who want to stay in the warm cab in the winter and just turn the switch on the dash on-the-fly to autolock the hubs (that would be me as well). I can advise you on repairing the existing hardware because that's what I did. Look at the PVHS at the bottom of this picture - it is mounted on the passenger fender well.


This would also be called the Electronic Shift On the Fly (ESOF) module. It is a common vacuum leak after 10 years and I had to replace mine when I bought the truck. I also had to trim my vacuum hoses to the hubs by about 1 1/2" right at the point where they connect to the hubs. Cutting the vac line is done after you inspect it and find cracks and other wear marks on the tubing.

The A/C only went to the defrost vents when I tried to go into 4X4, and the 4X4 didn't work - that was the symptom of bad vacuum lines to the hubs. The A/C went to the defrost vents full time - that was the symptom when I had a bad PVHS (ESOF module). Other leaks in the vacuum lines can cause nothing but defrost, you just need to plug the vaccum lines one at a time until you find the problem.

 

Great function and flow drawings. THANKS. Still no luck yet even after disconnecting at the PVH and sealing. So I think that m,eans I have a leak under the dashboard somewhere. I have a couple questions.

1) Is the AC vacum reservor (item 15), the same reservor as shown in the other drawing?

2) Does anyone know where the vacum control motor-Panel/Defrost door (item 1) is located? I may just engage it manually untill I can find the leak.

3) There is a vacum motor near the passenger foot area. When I engae it manually I hear the airflow change but dont feel any difference. Does anyone know which vacume motor this is?

Thanks
Doug

 

It seems the problem "MAY" be the ESOF module. The ESOF has a vacum line going to it from the vacum resivour to it, and one coming from it which goes to the hubs. When I disconnect the vacum line from the vacum resivour to the ESOF and plug it the air flow changes from defrost to vent. But when I connect the vacum line to the ESOF and plug the vacum line coming out of the ESOF the air flow does not shift from defrost to vent.

 

The ESOF was the problem. $80 for a new one but well worth it to have cool air blowing on me instead of the windshield. One just can't have to much ac in texas in the summertime. In fact, when it gets below 100 degrees in the summer here.................we call that a cold front!

 

Yup... well worth it to me to keep everything installed and working. You don't have snowy mountains like I do, but it's still nice to keep that 4X4 shift-on-the-fly.