What the guy told me at the dealership was, it is a switch that deactivates the ABS when in four-wheel-drive. Sort of what you were saying. That way the brakes are working under the normal braking system when in four-wheel-drive. Sounds good! Not sure if that’s 100% accurate but at least we now have a way to get it replaced!

 

Thank you for that bit of information, I have the factory books I purchased on ebay and I would like to research that. Had not heard of it which is not real strange.

 

I thought about buying those manuals, just haven’t pulled the trigger!! Let me know if you find out anything in those manuals about that switch! I’m curious to know if there’s anything in them about it. Thanks in advance.

 

Montana; I did some checking and your unit is a 96, and mine is a 99. I do not have that 3 pronged vacuum switch on my transfer case. I have spent about and hour in the factory manual and came up dry.
When I first got my Blazer I subscribed to alldata for a year; I found for me that it was still hard to learn what you wanted to know. So purchased the factory manuals. Yes they have been helpful; but I find them very frustrating to use. If you are researching something and get a thread going on it. It does not give you a page number; you have to go back to index and look under the noun name. I am sure there are people that have no problem with the system; I am just not one of them. I have better luck with goggle and Blazer forum. Would I buy them again, yes. But To me they are still a lot of work. Thank you for taking the time to reply to my question. I live in Hawaii and wreaking yards are not here that I have found. My four wheel drive does not work and the house is sold and I will be taking the Blazer back to Oregon with me. I have the fuse pulled for the 4 wheel part and really don't need it here for what I do. So when you said that the switch was connected to ABS system it got my attention, and it is something that I will have to proceed at a later date. We have (you pull it yards) there and should find cheap parts to carry on.

 

I have an issue I may have created. My 4WD actuator (under the battery) is engaged (holding vacuum, locking front end) when the push bottom is in 2 hi. And if you push 4 hi, the actuator releases. Here is what I’ve done: replaced the 3 prong vacuum switch on the transfer case, and replaced each of the three vacuum lines one at a time to ensure they went to where they were originally. I did this because 4WD would not engage due to vacuum leak, after repair I had great vacuum, but it seems to be applying vacuum when it isn’t supposed to and is releasing when it should be engaging. Any ideas what a did wrong?

my configuration has one vacuum line going directly from the T-case switch to the actuator under the battery, a second that is split by a t between the transmission/transfer case and appears to be just a vent up by the trans dip stick. And a 3rd vacuum line running up to a t by the brake booster, appearing to have one side of the t go to the fender and the other side going to the manifold.

thank you for your help guys!