Ive read numerous threads about issues with the 4 wheel drive system and have leaned a great deal. I haven't found the answer to my question regarding power to the vacuum solenoid. My system works fine when it works, but it works only intermittently. I have vacuum to the actuator, however, regardless of my switch position the vacuum never drops to allow the IWE to engage. Ive tested the plug to the solenoid and the voltage never changes. If I plug/unplug the power I can hear the solenoid function and it works as it should, i.e., vacuum drops to the line going to the IWEs. Ive bench tested the shift motor and it works, (on the bench) .. and i can hear it working ..(or at least trying to work maybe) installed on the transfer case .. when I switch between 2 and 4 wheel drive. I believe my problem lies either with the switch or the shift motor .. even thou the shift motors works in the bench test perhaps it isn't able to make the actual mechanism work when mounted to transfer case. All that said to ask .. does the shift motor position cause the solenoid to activate .. or does the solenoid activate solely by the dash switch .. is there a relay that works the solenoid ..

2010 Ford F150 FX4

 

Obviously nobody replied here, but did you figure it out yet? I realize this thread is over 2 years old, but my 4wd service icon appeared today and I’m gonna need to trouble shoot. Not a good time for it to act up, I don’t have a heated garage and I also do some snow plowing in the neighborhood.

 

the problem is computerized 4X4 is nothing like mechanical 4X4 that most people are used to.. the computerized system needs another computer to diagnose what is wrong.