Need help with front locker

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May 3, 2019
Minnesota, USA
New to the forum. Have referenced it for multiple things though. I need some expert help here. Got a 97 80 series. The front locker wont engage. I have spent a few hours looking for info, so far nothing has been my issue. As far as i can tell, the relay in the box, pass kick panel, does not click. So no power to the actuator. Is it common for these to go out? Or am I not understanding how it all works? Does power have to go thru the actuator before the relay works? Do the only run the ground side? I know power leaves the switch, and makes it to the circuit board. Beyond that, i lose it. Im not super tech savy, i just know basics. All im asking for is help on a startin point, or if i need to find a new control box for the lockers.
The actuators contain limit switches that cut power once the actuator moves to either the full on/ off position. The limit switches can keep the relays in the locker from activating (no clicks). The FSM has a test where you can use a 9V battery to connect directly to the actuator to see if that functions.

You can find an electronic version of the FSM here:

So, i tested the actuator. It works fine both ways. Moves freely. Is it possible that the 4wd ecu is at fault?
If you mean the Diff Lock ECU, yes it can fail like any other part. I would say that would be rare but I believe it can be opened up and inspected and relays tested individually. Before doing that I would inspect and test the wiring harness. The harness connects at the actuator going to another connection under/near the cruise control actuator on the passenger side inner fender.
Relays are not my strong suit. Far as i can tell from poking around, they all uave their necessary power and ground. It gets difficult testing controls when the knob is on the other side, and for whatever reason, the rear is finicky. Works fine, just stubborn. So, makes it a challenge to actually track changes. 4 relays, guessing one for on, and one for off on each locker?

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