4x4 Switch (2000 Chevy Blazer LT 4dr 4.3L)
#11
01-16-2019, 09:16 PM
Update
Update: So i got my new switch installed. Still no lights. Any suggestions on what to check next? FYI i do have an issue with a relay inside my glove box. Theres a constant ticking (like turn sigal). could this be related to why the switch is not functioning?
#12
01-17-2019, 06:20 AM
Time to start testing instead of replacing unnecessarily. There is plenty of wiring information for the NP236 (NP8) Auto4wd transfer case available throughout the forum as well as specific Tech Articles written on troubleshooting this system in its various forms in the Tech Article (DIY) section. You will find a link to an index of Tech Articles in my signature below.
To the original question concerning the switch. The 3 button switch is vastly different inside as compared with the 4 button switch. In the 3 button switch, there are 3 separate pairs of wires connecting the buttons to the TCCM behind the passenger footwell kick panel. In the 4 button switch, all 4 buttons communicate through just two wires by connecting various different resistors inside the switch when a button is pushed. In this setup, the TCCM sends out a particular voltage on the reference wire and monitors the voltage on the return wire. When a button is pushed, the voltage changes. Both switches can easily be checked for proper operation with a multimeter using the available wiring diagrams.
My first course of action would have been to check the various fuses for the 4wd system, specifically the ATC fuse in the underhood fuse block and the 4WD fuse in the instrument panel fuse block (located on the driver side dash accessible with the door open). If the fuses are good or even if you found a bad fuse, next I would pull the passenger side kick panel to gain access to the TCCM, remove the connectors, and inspect them for corrosion. For whatever reason, these connectors like to corrode and can cause all sorts of weird problems with 4wd activation.
As far as the clicking behind the passenger side dash, that may be the TCCM, but could also be the flasher relay and could indicate an issue with the hazard switch (common problem). We can tackle that once you get your 4wd system sorted.
To the original question concerning the switch. The 3 button switch is vastly different inside as compared with the 4 button switch. In the 3 button switch, there are 3 separate pairs of wires connecting the buttons to the TCCM behind the passenger footwell kick panel. In the 4 button switch, all 4 buttons communicate through just two wires by connecting various different resistors inside the switch when a button is pushed. In this setup, the TCCM sends out a particular voltage on the reference wire and monitors the voltage on the return wire. When a button is pushed, the voltage changes. Both switches can easily be checked for proper operation with a multimeter using the available wiring diagrams.
My first course of action would have been to check the various fuses for the 4wd system, specifically the ATC fuse in the underhood fuse block and the 4WD fuse in the instrument panel fuse block (located on the driver side dash accessible with the door open). If the fuses are good or even if you found a bad fuse, next I would pull the passenger side kick panel to gain access to the TCCM, remove the connectors, and inspect them for corrosion. For whatever reason, these connectors like to corrode and can cause all sorts of weird problems with 4wd activation.
As far as the clicking behind the passenger side dash, that may be the TCCM, but could also be the flasher relay and could indicate an issue with the hazard switch (common problem). We can tackle that once you get your 4wd system sorted.
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