ok i have a 2000 4x4 blazer 6.3l and its been snowing here in IL and earlier today it was working fine when pushing the button into hi lo or auto 4wd. a few hours later i go to use it again and i pushed the 4 hi button and it just flashes and the same for the auto 4wd and 4 lo any one kno why this is and it doesnt engage the front wheels thanks

 

Did the service 4wd light come on? Have you been through a lot of deep snow and packed up under the truck?

 

my guess would be that its the vacuum actuator switch located on the firewall they fail commonly and cause the lights to flash without the service 4wd light coming on ive had this part go twice on me with the same symptoms as you have

 

Hey sry I just noticed the 6.3 haha it's a 4.3 and I went through a couple deep drifts in my driveway haven't looked under and my dads painting a car in the heated garage. And do you know why the vaccum goes out just wondering

And there was no service 4x4 light on either