4x4 issues
 

Hey guys, I'm having an issue with my 97 F150 4.6 4x4. When I switch it to 4H there is I clicking sound before the 4x4 dash lights up. The actuator does then pull in and sometimes engages but not always fully. But when I switch back to 2 wheel drive, nothing happens. The dash light stays in and stays in 4 wheel drive. I have checked the vacuum at the actuator and have vacuum as I should. But instead of the vacuum changing once switching back to 2 wheel drive the 4H line stays active holding it in 4H. The only way it resets is to shut off the engine an then restart. Any ideas?