Hello, I have a 1999' S10 Chevy Blazer my question is... on my dash board I have the auto 4x4 switch that has the 4 different buttons on it. The lights just flash when I switch to 4H or 4L and even when I switch to auto 4x4 the light just flashes. I have checked the actuator under the battery tray all is good there noticed that the vacuum line had sone dry rot to it near the manifold area where the vacuum lines runs to the transfer case it self. So I replaced the entire vacuum line and tried that and the lights still flash on the on the dash board switch. I went to the passenger side of the blazer and pulled off the module and cleaned both of the wiring harnesses and placed it back together. Once the switch just flashes. I have read some forms about the vacuum switch that is on the top of the transfer case it self... here is my question are there 2 different types of transfer cases made in that year only reason I ask id my transfer case doesn't have the 3prong vacuum switch that I have read on other forms here. On my transfer case there was a nipple that the vacuum line ran to from the actuator... I can hear it shift when I switch it from
4H to 4L its just the light keeps on flashing. if someone has any in site on this please get back to me. I'm very mechanically inclined and do most of my repairs on my vehicles but, this has me stumped omg.

 

if you know what selection its in, shut the truck off then move the dial to that setting then turn the truck on. we just had a envoy come into the shop for the same thing. it was stuck in 4low and looks like someone put it in 2wd with the truck off and confused the computer.

so if youre in 2wd put the selector to 2wd then start the truck up and see if it works. just a idea

 

Hello, the Chevy S10 Blazer doesn't have the dial type of switch it has a push button set up with 4 different buttons on the dash. But, thanks for you reply.

 

You probably have the NV236 transfer case (should be a metal tag identifying it). Your vacuum switch (actually solenoid) is in the middle of the firewall (at the top) in the engine compartment instead of on the TC.

EDIT: See this thread https://blazerforum.com/forum/tech-a...rmation-41198/