4x4 inop NP243

[heavrolet98]

I just traded of my 97 K1500 Z71 with a NP241 for a 97 K2500 with a NP243 and the 4wheel drive is inop. When I turn the key to the on position all the lights come on and then go off like they should including the 2hi, 4hi, and 4low lights on the push button shifter. Once I start the truck none of the lights on the shifter are on. If I push 4hi I can hear a clicking in the dash and I can hear the motor in the transfer case working and the 4hi and 4low lights flash twice then sometimes they both stay on and sometimes they both go out. When I push 2hi I hear the same clicking noise and the transfer case motor turning but half the time the 4hi and low lights will flash twice and stay on. No matter what I do the 2hi light will not come on at all once the truck is running but like I said the bulb flashes on when I turn the key to the on position without starting the engine so I know its not blown. I really just want to make sure I'm not driving around in 4wheel drive.

 

[THEFERMANATOR]

Sounds like either a abd encoder switch in your transfer case encoder motor, or a bad dash switch.

 

[heavrolet98]

what is a abd encoder switch?

 

[THEFERMANATOR]

what is a abd encoder switch?

I mispelled it, bad encoder motor which is the assembly bolted to the transfer case where the linkage would normally be at.

 

[trouttrooper]

Doubt your driving around in 4wd. Easy check, just make a sharp left or right turn in a parking lot and see if the front end starts "arguing" with you.

The dash switch assemblies have been known to go bad. Even though they light up on startup like normal it could still be bad. If you have a junkyard close by you could grab a switch assembly there and see if it works.

 

[great white]

I'm betting on cold solder joints on the board.

Mine did similar shenanigans.

Pulled it apart, hit the board joints withe iron and all has been well for the last year...

 

[heavrolet98]

On what board? How do I check for this? Any pics available?

 

[great white]

On what board? How do I check for this? Any pics available?

It's the printed circuit board inside the switch itself.

Remove the switch from the dash and pry the cover off the switch. Go slow, work the tabs off the nibs and it will come right off. Examine the solder joints where the wiring connector pins are on the board. If any of the pins rock back and forth you've got a bad solder joint. If you see "voids" around the pin in the board or you can see the circuit trace around the pin on the pcb because of the voids, its a poor quality joint and electrically suspect.

Simply take a low wattage soldering iron and remelt the joints one by one. Fill in any voids. Make sure you use rosin core solder and not acid (plumbing solder) core. Do not move the pin rpior to the solder cooling or you will get what is a "cold solder joint". Cold joints are electrically suspect as they have poor conductivity (bad contact) or high resistance.

A high quality/proper joint should be shiny silver once cooled.

Don't have any pics available though.

This is a common problem with most gm electrical parts and modules of this era ( crazy wipers anyone?) since they were almost all "henco en Mexico"'( made in Mexico) for cheaper labor costs....