94 Ranger help diagnosing 4x4 shift motor
 

Hi and thanks in advance.

I have a 94 Ranger 4.0 w/manual trans. Started it up one evening and the 4Wheel and 4LOW lights were both lit up on their own. I pushed the 4Wheel button to turn it off and heard the shift motor move. Both lights stayed on. Pushed 4LOW, heard the motor again, both lights still on. After that, no matter what I pushed or how many times the motor never moved again and the lights remained on.

I unplugged the two right connectors to the module and ran a self diagnosis. Led blinked. Tested the 4 Wheel button lights, those work too. Fuses good also. Disconnected battery for a while, issue still present. Removed shift motor to check position, it's on 4LOW. Reinstalled and tried to back probe Orange and Yellow wires. Could not get a decent connection so I removed the shift motor and ran direct voltage to the Orange and Yellow wires on the motor, then reversed them Yellow + and Orange -. Motor turned both directions no issues.

Next day button lights no longer light up. Diagnose module again, all checks ok, but still nothing is working. Triangle shaped shaft on case has a spring like resistance, but it turns. With a friend pushing the 4Wheel button, I have voltage from the Orange wire that connects to shift motor. Pushed button again expecting voltage at the Yellow wire this time, but that didn't happen. Voltage supply still coming from the Orange wire only. So I'm confused as what to do next and what my issue might be.

Thanks everyone for any tips or insight on this issue.

Welcome to the forum

In the 4x4 controller are two 5 pole relays, one for orange wire, and one for yellow wire
When relays are off both wires should show as Grounds(-)
To move the shift motor the 4x4 controller only has to activate one relay changing it's wire to 12volts(+) because the other wire is already a ground(-)
So clockwise or counter clockwise rotation depending on which wire is is 12v(+)

The other 5 wires on the shift motor are position sensors/contacts, the 4x4 controller will not move the shift motor(activate a relay) if it doesn't "know" the current position of the shift motor via the contacts
The 4x4 controller is what activates the 4WD lights on the dash, there are no sensors inside transfer case, when 4x4 controller "sees" the contacts in correct alignment for 4high it activates that light bulb by grounding it, bulbs get 12volts with key on but are not grounded

4x4 controller could have a bad relay, no self test for that
4WD lights should flash if you try to shift and shift motor doesn't move
And because both light were stuck on I would suspect controller issue

Thanks Ron for the in-depth information and schematic. Two separate relays, that makes sense re: no power from the Yellow wire. I wonder if it's possible bad contacts in the shift motor could cause the same issue? Years ago both lights came on their own. This happened on two different occasions, but I wrote it off as being related to the cold weather as it quickly went away and everything still worked.

look here: https://www.therangerstation.com/tec...e-shift-motor/

Picture 5 shows the contact plate, pic 6 is the contacts, only 5 are used
Plate spins with transfer case shifter rod, making and breaking contacts

The 4x4 controller controls the lights not the contacts
Controller turns on a 4WD light when contacts show correct position for the selection, not before, i.e. pressing the button doesn't turn on a 4WD light
Pressing button activates 4x4 control, it then looks at current position, 2WD, 4H or 4L, it then activates a relay to move shifter to new position, once contacts shows its there it turns on(or off) 4WD light

Hi Ron, That's one of the two threads I read that helped me understand more how things work and how to diagnose with my limited knowledge. Understanding the module controls things (not the buttons or the motor), my concern is the relationship between the module and the motor's contacts. I should add I can hear the module click one time when I press either button.

Thread reads "and by a series of open/closed circuits, the computer can tell where the selector shaft is pointing. This is pretty important because the computer has to tell the motor when to start and stop. If the computer doesn't know what position it is in, it will default to a fail-safe mode of doing nothing" - and nothing is what it's doing, no lights no movement, nothing. Could the contacts be in a worn state where the module can't figure out what to do with the lights and the motor? I could buy a module, though it would be used because of the age of this vehicle. Used electronics have their own uncertainties, but I may have no other choice.