2000 Blazer 4x4 Not Engaging
 

I recently bought a 2000 blazer LS 4x4. My main issue right now is that the 4 wheel drive will not engage. The Buttons to switch it to 4x4 will light up, although i have had to bang it a few times to get any lights to come on it. My question is could it be the switch? the actuator? How would i test them? Where would i start? I appreciate all and any help.

The Tech Article (DIY) Index should get you started.

that happened to me, i would push the button for it to engage in 4 wheel drive and it would just blink and flash red... i took it to a professional and it turned out just the switches weren't working for some reason, im pretty sure thats all it is, easy fix though kind of expensive to get fixed.

Easy enough to check before just throwing a new one at it.

The NV233 (3-button switch) wiring diagrams are posted in a few different articles in the Tech Article (DIY) section. The switches in the NV233 controls are momentary straight through contacts with wiring leading straight back to the TCCM.

The NV236 (4-button switch) wiring diagrams are also posted in the Tech Article (DIY) section. This switch only has one wire that leads back to the TCCM and relies on a series of parallel resistors in the circuit to modify a reference voltage telling the TCCM which button was pushed.

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I have been researching and reading alot about vaccum problems could cause this. My heat only blows out of the front vents and not defrost or floor, could these be related because I read alot of the hvac is vaccum controlled. My switch has never showed a red light that i have seen.