How to change a vacuum switch on a for 4x4 2000 Chevy blazer?

i have a 2000 chevy blazer that the 4x4 does not work right. it has the push button system. when you try to put in into four wheel most of the time it will go in(sometimes not), but it will not go back to two wheel. when i push the button, the indicator lights will flash, then turn off(you can here clicking underneith the frount end) and the service 4x4 comes on the dash. i have got to turn off the car for a few hours, then when i start it, the lights are back on. i have got to do that a couple of times before it will go into two wheel again. i was told(not by a macanic), it was the vacume switch. but i welcome any suggestions to what other things it might be. but i want to know how to change that switch, so thanks for the answers.How to change a vacuum switch on a for 4x4 2000 Chevy blazer?did you try moving the vehicle back or forth a few meters before trying to shift from 4wd to 2wd? but i guess you do have some kind of problem with the system as you are getting the service 4wd light on , in the dash. before you replace any parts be sure to check the vaccum hoses of the 4wdsystem. if its cut it would nt get enough vaccum to activate the 4wd actuator. Hint: Remove the battery, the battery tray to have have access to the vaccum hoses leading to the actuator. You need to put the vehicle on the ramp to have access to the vaccum hoses leading to the transfer case.