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Discussion Starter #1
Won't engage into 4X via dash switch. Exhausted search option so:

Dash mounted switch, Warn hubs, vaccum lines unhooked and plugged, checked/replaced fuses and relay under hood, replaced motor on T-case, replaced bulb in dash, 4X4 light comes on with key so works, can manually shift it into 4X with little shifter motor off so it's not the t-case.

Thinking it's the switch but not sure how to bypass it (jump between wires) to make sure. I've taken it apart and cleaned the contacts, all looks good and pretty simple.

Not sure where else to look. What other components are there (switch, relay, fuse, shift motor):confused:

Thanks!
 

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I believe the GEM module is involved in the operation.
 

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Resident Idiot
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It looks like there are only two wires that go to your switch. One is the input and the other is the output. The difference is it goes through a different set of resisters and then to the control module. It then probably senses the different voltage and then determines if you want it in two or four wheel drive. The only real way to test it is to check continuity trough the switch on each setting.
 

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Resident Idiot
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well four wires if you count the ones for illumination. You will want to check resistance on the Dark blue and the white/light blue wire. You will have to check it in each switch position.
 

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Jackleg Mechanic
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what resistor did you replace, ie where is it located?
 

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Discussion Starter #6
Gem has been replaced.

Will check resistance, thanks THORGUY57, helps to know which wires (need to learn to use the dang ohm meter someday anyway!)

Not resister but replaced fuse and relay under hood next to fuse box. Both were good but changed anyway. Not sure where resistor is. Neither hi nor low work via switch.
 

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Resident Idiot
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The resister is built into the switch itself. If they are bad the switch has to be replaced. Also check for powder going into the switch (dark blue wire I believe) and also ohm out between the switch (the other white with light blue wire I think) and your 4 wheel drive module.
 

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Jackleg Mechanic
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Resister was not what I meant to say, on my truck there's a relay box up next to the left battery that has two relay's in it that control the 4wd. I had the same symptoms that you describe and after replacing those two relays my problems were solved. Maybe yours has that little relay box too.
 

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Discussion Starter #9
Don't think I'm getting power to the switch (at least can't confirm with test light) BUT if I manually turn knob on T-case and on motor and attach motor to t-case it will stay in 4X without light being on. If I switch dash knob to 2X it will switch out of 4X but not back in... I replaced both relays in engine compartment with used ones but will try new ones. Not getting continuity between dark blue and wht lt blue wires in 2 or 4 hi but am in 4 lo. Where is the module located?
Going to be out of town for a few days so will work on it again next week. Thanks for the ideas thus far.
 

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Resident Idiot
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I will look that up when I get home for you. If you are not getting any continuity (open circuit) between the two wires in 2 or 4 hi that is definitely a problem. How it can switch from 4 hi to 2 wheel drive without any continuity on the switch is a mystery that is for sure. That really doesn't make any sense. You said it doesn't shift into 4 low is that correct? Did you make sure your transmission was in neutral before doing this? Sorry just have to ask. Some people don't realize it won't go into 4 low unless your transmission is in neutral.
 
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