Question 4x4 Solenoid testing

[JHargrave]

I have a 2006 F-250 6.0 4x4 with 147500 miles. When I put it in 4x the a/c deverts to the defrost. I've vacuum tested the hubs and they hold a good vacuum. Is there anyway for me to vacuum test the solenoid itself? thanks for any help.

 

[DaveBen]

The Defrost mode is the default mode. This means that you are not getting vacuum to the heater controls. You can check to see if the solenoid is passing vacuum by pulling one hose at a time. I am not familiar with this solenoid, so I am not sure if it passes vacuum or switches vacuum. If is does nothing, you get defrost.

Dave

 

[dpantazis]

sounds like you have a vacuum leak somewhere.

how are you testing the lockout hubs? i would check at the hub with a mightyvac and short piece of tubing to actuate the hub, then at the solenoid to check for leaks between the solenoid and the hub then upstream of the solenoid to check the solenoid.

solenoid on the passenger fender? you could probably put a mighty vac on the vacuum line supplying it, then switch the 4WD switch. might not have enough to really pull the hubs, but at least should hold some vacuum to diagnose.

good luck

 

[JHargrave]

yeah its the solenoid on the passenger side fender. I pulled the lines apart at the plastic connector and tested the hubs that way and it takes awhile to create the vacuum but it holds a good vacuum at 25inch, I haven't had time to test right off the hub yet I'm working nights. I'm praying that its not my hubs I really don't have the $800 to replace them

 

[dpantazis]

if it holds pressure from the output side of the solenoid to the hubs, then i would not worry about checking them at the hub. you basically tested it all the way to the bottom.

i suspect that you have a funky solenoid or broken connection upstream of the solenoid.

 

[rocketdog]

this is exactly the problem I am having with my 2002 Superduty. Blows fine through A/C vents. Then I put in 4x4 and starts blowing through the defrost vents.

Take it out of 4x4 and it takes about a minute for it to start blowing through A/C vents again. ESOF don't work either and hubs are frozen so I can't lock them manually. I took the hubs apart last year, cleaned and re-lubed and the 4x4 worked for a couple of months and then stopped again.

I am going to do some vacuum checking this weekend.

 

[DaveBen]

You have a vacuum leak when it is shifted into four wheel drive. Look at the vacuum lines going to the hubs from the frame. They usually leak there, but it can be any where. Good Luck!

Dave