This sounds like a YJ Jeep issue, I eliminated the vacuum actuator by installing a heavy duty choke style manual cable attached to the vacuum actuator arm, that way I can lock the front diff when I wanted. Make sure you cap off the vacuum line, otherwise your engine will run poorly.
The vacuum actuator is on the right side of the axle. The electrical switch is on the actuator. The vacuum switch is on the top of the transfer case.
on the front axel
The vacuum actuator is either in the fender or under the battery. The actually diff actuator is on the back/bottom of the front diff. Mine (2000 blazer) is under the battery. It sucks to get to. If you check the actuator and it doesn't move at all, check the vacuum, if it's not getting vacuum, check the switch on the top driver's side of the transfer case. It sends vacuum to the actuator. It has three vacuum hoses coming off of it. It costs fifteen dollars at autozone and usually greatly improves the performance of the acuator.
There is no vacuum switch. There is an electric actuator on the front left of the front end assembly right in front of where the cv shaft goes into the differential case and an electric actuator on the rear right of the transfer case.
On a Dodge Ram, it runs from the intake manifold, to the switch on the transfer case, to the front axle shift actuator.
The actuator of the Dodge Ram 4x4 is located on the top of the front differential. Depending on the year, the actuator is either vacuum or manually operated.
Differentials were locked by vacuum pressure on a actuator on the front axle, if there is a problem with this actuator or with your vacuum system the front axle will not engage. You may want to remove the acy=tuator and clean it out, ot locate the vacuum leak in your system.
The waste gate is part of the turbocharger. The actuator is screwed into the front.
the vacuum valve on the transfer case takes engine vacuum, and uses it to engage the central axle disconnect on the front axle when the case is shifted into 4wd. this is also the cause of the slight delay between shifting in/out of 4wd, and the 4wd indicator light turning on/off - real world, on an older Jeep, it takes up to a few seconds, sometimes, for the engine to pull enough vacuum to shift the front axle actuator. Both the vacuum switch, and the vacuum actuator on the axle are common failures, and there are a number of kits on the market to convert the front axle to use a cable actuator
If it's vacuum (has hose) just apply vacuum.
vacuum actuator is bad, there could be a hose that is missing, the hose might be weathered and cracked or cut, vacuum actuator might be all gummed up and crappy lookin on the inside, a simple cleaning might work, other then that a new actuator might be a need, not hard to install though
It will either be the vacuum solenoid (actuator) located under the battery tray or the electronic solenoid on the front differential. Most commonly it is the vacuum solenoid (actuator). Once you take the battery and battery tray out you will see the rubber bladder of the vacuum solenoid (actuator) if it is torn or busted replace it. Check the vacuum solenoid (actuator) located under the battery and battery tray. It could also be the vacuum solenoid located on the firewall above the distributor (approx. 3"x1")