I have a 2000 Blazer 4.3 with the NP233 T-Case. I seem to have a phantom 4WD Switch. I was at a concert over the weekend and when I was pulling out of a muddy field, I shifted into 4WD like usual and I hear the TCCM click, the encoder motor shift the case and I could feel and see the front wheels pulling. When I looked at the switch on the dash, I see that the 4Hi light is not lit, and no light on the switch is lit. I thought, "well it is just a bad switch, I'll deal with it later." About 5 minutes later while sitting in traffic, I see that the 4Hi light is now lit, so I got confused.

After the weekend, I did a little troubleshooting with what I could. Here is what I've got:
2Hi: Light is lit always when in 2Hi
4Hi: Light will sometime come on, sometimes it won't when pushed.

• T-Case always shifts and engages no problem
• TCCM always clicks
• Front Differential always engages

4Lo:Shifts no problem and works just fine


Is it possible that I just have a bad switch, or what? Any help/ideas/directions you guys can provide will be greatly appreciated! Thanks again!!

 

I believe that the light is triggered by the electronic switch located on the front axle. Maybe the switch is sticking? Or possibly the cable is not always filly engaging the front diff; just enough to make it pull, but not enough to trigger the switch.

 

Alright, I will check on the switch, I see that it is very similar to the vacuum switch on the transfer case. I'll check it for movement and then report. *Edit* The switch moves freely. so that leads me to believe that it is the cable. It is not kinked or anything, I did not check for complete retraction of the vacuum actuator but will do that later. What else can I check? *Edit 2* The Light on the switch always lights up when I shift into 4Lo. I've done it a couple times before I shifted into 4Hi, and it works as designed.