I know 4WD questions get asked a lot on here, but I couldn't find anyone that had the same problem as me on here.

Anyway I drive a 2002 Blazer 2dr. I bought it about a year ago and the 4WD was working fine. It has the push button 4hi/4lo.

I had the Heater Core replaced around September of last year and when I got it back the 4WD indicator wasn't even lit up.

The reason I brought up the Heater Core is right after it was replaced the 4WD stopped working and I don't know if there's a connection between that.

So normally the light is on 2hi and it stays there until I engage the 4WD...Well the 2hi isn't lit up and when I press 4hi/4lo nothing happens and it won't engage like it did when I first bought it.

 

Sounds like they forgot to plug it in. Pull the two screws above your intrument cluster, and the whole trim piece just pulls off. check to make shure it's plugged in. And reassemble.

 

It's plugged in. Still no status light and won't engage.

 

May be something as simple as the switch that is in your cab. Know any friends with the same push buttons? Try switching them out?

-hp

 

3 or 4 button switch in the dash?

Wiring schematics for both are located in the Tech Article (DIY) section. You can test the switch for proper operation as well as testing for the proper inputs from the TCCM at the plug to the switch.

 

It's 3 button.

 

Check out THIS THREAD for the wiring diagrams. If that doesn't work, CLICK HERE. (stupid www. vs. non-www.)

 

Vacuum operates the actuators on the heater flaps
(def, floor, etc)

Vacuum also operates the actuator that pulls the cable going to the 4WD case

If they left a hose off, it's leaking vacuum

OR look on driver's side valve cover for a small hose that comes up to a T connection on the upper firewall close to the fender. That leaks often. Check vacuum at that line or just replace the thing for three bucks.