4WD mystery part!!
 

If anyone can help with this it would be much appreciated!!

I have a 96 blazer. right now I have a manual valve hooked up I can open and close to control the cable on the 4wd actuator. The vacuum hose off of the actuator went to a part that was a 2 pin connection in the back that I believe to be the problem. I can not find this part anywhere or even the name. Even with the part number off of it. This is the part number 15763461 and I attached some pictures. Thanks in advance!

https://cimg5.ibsrv.net/gimg/blazerf...3e8cc8bb1f.jpg

Looks like some sort of vacuum operated switch.

My Toy is built out of a 92 Jimmy and has a vacuum line mounted switch like that T'ed in the front diff actuator vacuum line but the mounting end is different if I remember right mine has a hose barb end.
As far as I know it tells the tccm that there is vacuum running to the actuator, If the 4WD works while bypassed I would think the problem is with the vacuum switch on the transfer case.
The only thing I could find with elec. connections is the switch for the 4WD drive light but the ones that I found has attachment threads

It is some sort of vacuum switch. Actually favors more of an oil sending unit to me. Two things I don't understand is if was to turn on and off vacuum where would the vacuum go? I would still be capped off by this. Even more so I don't understand how I can not find this part. I will look towards some older year models though. Maybe this is something someone rigged up although there are electric connections for it.

I can't find this part in any diagrams or any reference anywhere online to that PN, but here's what I can tell you about its function. It is a simple vacuum switch. It either is electrically open or closed with atmospheric pressure (vented to the outside) and the opposite (electrically closed or open) when vacuum is applied. The only thing it does is provide a method of electrically sensing when vacuum has been applied to the actuator. It likely was used to illuminate a feedback light on the dash/console somewhere for when the front axle engagement system was fed engine vacuum.

It does not have any way of altering the pressure in the system. To accomplish that, it would be a vacuum solenoid (or valve) and would have one or more additional ports on it.

My old 4wd '85 S10 had a diagram of the drivetrain along side the floor shifter for the 4WD system. The front axle portion of the drivetrain would light up, triggered by a very similar switch in the vacuum system near the actuator. Putting the switch on an intermediate process in the system is kind of dumb as it does not indicate that the axle is actually engaging, rather that vacuum has been supplied to the actuator that is responsible for pulling on the engagement arm inside the axle. A much better location for this switch would be down on the end of the engagement arm in the front axle disconnect system such that it only triggers when the arm is fully pulled into the engaged position. But who am I to list common sense design when the bean-counters likely necessitated its location... LOL

On the 92 that I used it has two switches, the one in question and the 4wd light switch mounted on the front diff. I have replaced the one in question while playing with my 4WD and the bone yard is the only place I could find it

Where should this hose be going then? To a solenoid I would assume. I don't even see a part for this online. I do see for the 97+. Right now I literally have a valve from Home Depot to open and close this vacuum. What am I missing in the system to make this touch less like it should be?

Too lazy to retype
You should have a switch on the transfer case above the shift linkage that has 3 vacuum lines on it, input, out put and vent to release the vacuum in the front actuator vacuum line.
If you have 4WD bypassed check this switch

Yup, if you have to close off vacuum supply to the actuator with a manual valve, then there is something wrong with the "vacuum switch" (mechanical valve) that threads into the transfer case. This device has three vacuum lines attached to it, manifold vacuum, vent, and vacuum feed to 4wd engagement actuator. There is LOTS of information on this problem here as well as other places online. Have a look in the Tech Article (DIY) section for 4wd related threads. I have posted a few vacuum diagrams for the common configurations in that section and there are numerous other threads/posts by other helpful members out in the 2nd Gen Tech section.

Okay I will check my lines that they are in the correct place on the switch. If that doesn't help I will throw a new switch on it and see what I get maybe it will solve the problem. I appreciate the help for now guys!