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I have a 94 chevy k2500. It will not engage into 4wd high or

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I have a 94 chevy k2500. It will not engage into 4wd high or low. I have replaced the front actuator {electric} There is 5 prongs on the actuator but only three are used. I have power to 1 of those prongs. It had a electric actuator on it already, so when i got the "new" one I did get it from a junk yard. Could it be bad also or is there anyway to check it or is it something else?



1. Located the transfer case switch on the top of the transfer case, this switch will have two wires going to it. One wire will be Brown, this is Battery Voltage (B+) coming from the fuse block, the other wire is Blue and goes to the front actuator.

2. If there is B+ on the Brown wire, but no voltage on the Blue with the transfer case in 4x4, the switch will need to be replaced.

3. If there is B+ on both Brown and Blue, but no voltage on the Blue wire at the front actuator, check the wire between the transfer case switch and the front actuator for opens.


At the switch located on the top of the transfer case, check power on the Brown wire. If voltage is not present, check for high resistance or a open wire between the fuse block and transfer case switch.

Edited by AMEDEE on 12/16/2009 at 10:57 PM EST
Customer: replied 7 years ago.
where exactly is this switch?
The switch? Inside the vehicle where you would press the button.
Customer: replied 7 years ago.
no button. shifter on the floor and no wires in there. where else?

Sorry for the delay!


Are there any 4wd lights flashing on the dash?

Customer: replied 7 years ago.
no lights on the dash, just the the light on the floor shifter but it doesn't come on and the bulb is good

1. Disconnect the actuator in front, with it in 4WD, and see if it has power and ground on the Blue and Black wires.

2. If no power on the Blue wire, then check for power on the Blue wire backprobed at the switch on the transfer case.

3. If still no voltage, then check for power on the Brown wire at the switch on top of the transfer case.

4. If the Brown wire shows no voltage, verify if the 4WD fuse is blown.

Power is supplied on the Brown wire to the switch and when put in 4WD, the switch on the transfer case closes and puts power out on the Blue wire to the actuator in the front. The actuator is always grounded, so when it gets power on the Blue wire, it should activate to lock the front end.

Here is also a TSB for this problem.


Drivetrain - Slow Or No Engagement of Front Axle


File In Section: 4 Drive Axle

Bulletin No.: 76-43-01A

Date: September, 1998

Slow or no Engagement of Front Axle when 4WD is selected (Replace Front Axle Actuator)

1988-97 Chevrolet and GMC K Models
excluding 1988-93 Models over 8500 # XXXXX

This bulletin is being revised to add information to the Service Procedure, add a new part number, and include schematics. Please discard Corporate Bulletin Number 76-43-01 (SectionXXXXXAxle).


Some owners may comment that the colder the outside temperature is, the longer it takes for the front axle to engage whenXXXXXis selected, or the front axle does not engage.


The front axle engagement actuator is a thermally activated component. Because of this characteristic, the time required for the actuator to completeXXXXXengagement is extended as the temperature drops.


Replace the front axle actuator and include the applicable wiring harness kit. Refer to the Parts Information in order to determine which wiring harness kit is needed.

1996 model trucks with a build date on or after January 2, 1996 are considered as "961". If the build date of the truck is unknown, verify the 3 character "axle code" on the front axle label in order to determine which wire harness to order.

This new actuator uses a motor to engage the front axle and is not affected by temperature. On 1988-93 models with a GVW rating over 8500$, the new actuator cannot be installed and the thermal actuator will remain the service part.


Customer: replied 7 years ago.
ok there is power and groung to the brown and black but not to the blue which tells us that it is the switch.I still have not located the switch I bypased the the switch and hooked the brown to the blue and it went into 4wd. Not the best idea to do because it will be in 4wd all the time, plus who knows what else will happen. I do not want any other problems than i have to have. Thank you for your help and i will get that fixed as soon as possible. There is 11 inches of snow here and i need it badly.



Sounds good!


I hope this helps. You can always accept my answer now, and repost back again later on if you have any more questions. If you want to discuss it some more just hit "reply", it's free to do so otherwise don't forget to hit "accept" and leave positive feedback if you found my answer helpful.





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