1994 Jimmy GMC 4WD.

Hi, First time here, I'm trying to help out a friend with his car. He has a 1994 GMC 4x4 Jimmy 4dr.auto trans, switch on fly. The problem
is this.When driving and go to engage 4WD, you push a button on the dash and it supposed to light up, but it does not. If you stop the truck in neutral(dash button for 4wd) will flash on and then you hear click noise like it engaged, again the light on the dash flashes then goes out and nothing happens.The 4wd. Low works fine.
Last year he had the same problem in the cold winter months, 4WD did not engage. In the summer,the 4WD would work and engage no problem all summer. Cold definitely has a bearing on it somewhere. If anyone has had a similar problem or any help let me know here. Thanks in advance
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hate to be the bearer of bad news but i had the exact same problem on my old 94 blazer and it turned out to be the encoder motor
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Thanks, what exactly is it and where is it. My guess is the motor that shifts it inside the transfer box????/

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I believe there is a 'solenoid' in the front drive shaft that in your year is quite defective. I don't believe it is all that hard to change out, and the '98+ is an actual solenoid and works very well. You should also check all your fuses just for fun.
~KJ~
The switch is on the top of the transfer case. The 'soleniod'

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neither design is an actual solenoid... i.e. an electrical coil energized to create a magnetic field, pulling in a ferrous metal actuator. the 98+ actuator is basically a small motor driven linear actuator. yep it works AWESOME!
-Bret

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Why do people do this all the time? The S-series trucks, like the one in question, use a vacuum actuator under the battery to pull a cable and engage the front axle. This actuator is controlled by a vacuum "switch" on the t-case.
The full-size trucks have the infamous electrically heated gas charged solenoid that's prone to failure...

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That's right. I had forgotten reading that. You all must remember I only wrench on an 85 K5, so just about anything I say is bull shit straight from another post mangled by my memory.
~KJ~ Disclaimer: I don't know Jack Schitt

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