This is my first post, so here goes... I have 2003 F150 with an electronic 4x4 switch. At first it would not engage however the indicator light lit up. After playing a numbers game it finally engaged. Since then when I get it to engage, it slips out of 4x4. I'm getting power from the transfer case and recently discovered that it is not engaging at the front diff. I pulled the hoses off the solenoid to see if there was any vacuum (left the supply hose attached). There was no indication of a vacuum from the solenoid. When I pulled the hoses off the passenger side solenoid there seemed to be a vacuum on that line. This did not happen to the other solenoid. Any ideas on what the problem is? Which solenoid engages the diff.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

 

Hi and welcome to the forum

One of the solenoids applies vacuum to the axle disconnect to engage it and the other to disengage it.
Do you have supply vacuum at both solenoids? Broken vacuum lines or a cracked vacumm reservoir behind the battery are quite common.

 

It appears that there is only vacuum on the left (facing the truck) solenoid. It sounds like the supply line.