Just got a 2000 Blazer LT with 4.3 for my son. It has the Auto, 2 hi, 4 hi, 4 low buttons. As long as it is in 2 hi the light stays burning steady. When you try to put it in Auto or 4 hi or low, the light flashes for whichever one you try to put it in. I have tried to change it in park, neutral, and when driving real slow. It does the same each time. What should I be checking?

 

I take it you mean that the 4wd does not engage when you try anything other than 2 Hi. If so, there is a vacuum switch under the battery tray that could be bad, or the control cable from the vacuum switch to the transfer case could be bad, etc. I'd invest in a Haynes manual and chase down the vacuum line to the switch, then the switch, then the cable. It sounds a lot worse than it is. The vacuum line could be shot (dry, brittle, disconnected), the vacuum switch could be malfunctioning, the cable could be rusted or broken.

 

Started checking today and al vacuum hoses seem to be ok. They all hold vacuum. Took the Vacuum Actuator off to watch it in operation with cable unhooked. Put it in 4 hi and the vacuum actuator pulled in. Switched it back to 2 hi and the vacuum stays in the same place. If I pull the vacuum hose off it releases the vacuum and it pops back out. Is that how it is supposed to work or should the vacuum release when you put it back in 2 hi.

With the cable unhooked from the Vacuum Actuator I tried to move the cable. The cable won't move. Should I be able to move it with it unhooked from the actuator?

 

Yes, you should be able to move it. Sounds as though your cable is froze up. Does the actuator move the cable when everything is hooked up?

 

When everything is hooked up the actuator won't move the cable. When I had it unhooked from the cable, when I hit the 4hi, the vacuum will pull the actuator in. If you switch it back from 4hi to 2hi, the vacuum keeps the actuator in. Should the vacuum relese or is that normal.

 

The engagement mechanism should be spring loaded in the axle which will pull on the cable thereby pulling on the vacuum actuator when vacuum supply is removed. The light spring in the actuator often isn't enough to return the actuator to its rest position. Since the cable is not moving, you have to free it up.

 

Replaced the cable. All is good now. Thanks for the help.

 

Glad you got it fixed! And thanks for the update.