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Electronic Transfer Case Motor Diag


ecgreen

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OK, I have been reading about the elctronic motors on on my transfer case and I understand the basics of how it works. It is not working right now, and I am a bit confused about how to go about the diagnostics here. Any help would GREATLY appreciated ('cause you guys are awesome):

The Deal:

-1989 Bronco II 2.9L
-Electronic transfer case worked fine when I bought it.
-The other day I went to put it in 4-low and no response
-Tried it multiple times and it finally worked (got it into 4-low)
-Now it won't come out of 4-low
-Both the 4x4 and 4-low lights are on.
-When I press the buttons I hear nothing, no click, no nothing
-I checked the 20amp fuse under the dash and it is OK.

Where do I go from here in testing? Since there is not sound at all, I am assuming the motor is not getting any power. I can't seem to find the motor on the wiring diagram though.
Help this FNG, you know you want to.
 


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Shran

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Tap into the big orange wire right at the transfer case harness connector with everything hooked up, and get a voltage reading off that when you push one of the buttons. You should be getting battery voltage there.

There is a troubleshooting checklist you can go through and it involves testing the shift module, wiring to and from it, the switches themselves, the speed sensor, and the shift motor. It is complex and there are a bunch of points of failure but the most common one I've seen has been the shift motor itself - I work through the checklist and get to that orange wire and get a weird reading, like 4 or 5v and basically the same symptoms you described. It ends up being a failed shift motor. I have had a supply of good shift motors so I have just replaced them instead of trying to rebuild them, but just FYI they can be fixed.

Just to save you some time, if you're getting weird voltage at that wire, it's a fairly safe bet that you need a shift motor. And, you can shift it manually with the motor removed and not be stuck in 4 Low.
 

RonD

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I don't think there is a fuse for the shift motor in 1989, it would most likely use a Fusible link hooked up to the starter relay(solenoid) in the engine bay
The starter relay has battery positive cable connected to one post, that's the main electrical 12v distribution, alternator, fuse boxes and a few other devices are connected there
The shift motors power wire would run to the Shift Module

The Shift Module would have a separate fuse in the cab fuse box, and module should "click" to activate shift motor, this module is usually located behind drivers seat, behind a panel, has a heat sink on it so "looks like" an amplifier
But not sure of its location in a BII

1994 and earlier Rangers are different, read here: https://www.therangerstation.com/tech/ford-ranger-4x4-module-diagnosis-1994-older/

You can remove shift motor and shift transfer case manually, and then test shift motor while its out

Its obvious which 2 wires are for the Motor part, the other wires are for position sensor in the gear box of the shift motor
You can cut the Brown wire that goes to transfer case, its for the electric clutch, but you should splice it back together after reinstalling the shift motor

So the 2 wires that go to the motor need to be 12v and ground to test motor, there are limits so the motor can only turn so far in either direction, and the motor does turn BOTH ways, just like power window motors
So 12v/ground will turn motor one way, then ground/12v turns it the other way, so you reverse polarity to change motors direction

The brushes inside these motors get worn out so motor stops working
Shift motor disassembly seen here: https://www.explorerforum.com/forums/threads/how-to-rebuild-4x4-shift-motor.123542/
 

ecgreen

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OK guys this is what I was looking for educated opions about where to start. I'll run with this info and post back later. Thanks!
 

ecgreen

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Well I took the motor out to try and get it into 2H manually. It won't go. How far do I have to turn that thing to get it into 2H? The pin to turn is like triangle and it was pointed at 4-low. Iknow have it pointed at 2-High, but the truck is still in 4-low.
 

ecgreen

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Also tried to test the motor with no luck. I grounded the center pin on the connector to the battery and touched a hot wire to the pins that go to the motor, No luck
 

RonD

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First MAKE SURE wheels are blocked, transfer case does have a neutral, and you have to shift to neutral from 4L, to get to 4H and then to 2H
(Neutral is directly across from 2H), between 4H and 4L)

So the shift rod only turns counter clockwise to 4L then it turns clockwise to 2H, it can not turn 360deg

To shift transfer case, pressure must be taken off the drive shafts, so try rocking the truck forward and backward a little, WHEELS BLOCKED, while trying to shift transfer case manually



There are 2 shift motor wires, yellow and orange usually
1 must be a ground and other 12volts, then motor will turn, reverse polarity to reverse direction the motor turns


There is no "common ground" on the shift motor unit, so not sure what the "center pin" is, but if it ain't an orange or yellow wire then it ain't the one to use to test if motor is working
 

ecgreen

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First MAKE SURE wheels are blocked, transfer case does have a neutral, and you have to shift to neutral from 4L, to get to 4H and then to 2H
(Neutral is directly across from 2H), between 4H and 4L)

So the shift rod only turns counter clockwise to 4L then it turns clockwise to 2H, it can not turn 360deg

To shift transfer case, pressure must be taken off the drive shafts, so try rocking the truck forward and backward a little, WHEELS BLOCKED, while trying to shift transfer case manually



There are 2 shift motor wires, yellow and orange usually
1 must be a ground and other 12volts, then motor will turn, reverse polarity to reverse direction the motor turns


There is no "common ground" on the shift motor unit, so not sure what the "center pin" is, but if it ain't an orange or yellow wire then it ain't the one to use to test if motor is working
I have been schooled! Thanks! I'll get back to you
 

ecgreen

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OK, got it into 4 hi at least.

Tested the motor in the way you described. It ran for a second and wouldnt run again after that
 

ecgreen

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It looks like someone has been in this case before. Is the shaft the the motor turns twisted at its base?
 

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ecgreen

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I am starting to think I should just get a good manual case
 

RonD

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There are "stops" inside the shift motor housing so it will only turn so far one way(4L), then you have to reverse the polarity to turn motor the other way(2H)

Yes, manual transfer case will have fewer issues but also no "shift on the fly", you should always stop to shift transfer case
If you go that route make sure you get the shifter and linkage, those parts are hard to come by

BW1350 or BW1354 manual transfer case up to 1997 will work for you, 1998 and up may not have speedometer cable hook up you need for 1989


The biggest issue with electric shift transfer cases are disuse.............they may only be used a few months a year, if that much, so brushes in the shift motor stick in place from disuse, so it was working in January but doesn't work the following December, "WTF!! piece of sh!t", lol

Best practice is to shift to 4low and back to 2WD once a month to keep brushes clean and lube spread out, just sitting in driveway, don't have to drive in 4WD..............unless you want to :)
 
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It looks like someone has been in this case before. Is the shaft the the motor turns twisted at its base?
it goes into a collar that is sort of twisted.

shifting 101
the motor turns the triangle shaft (via a gear)
the shaft puts pressure on a spring
the spring puts pressure on the collar
the collar moves the shift forks, or it tries to move the shift forks. they don't move if the gears have pressure on them.
that's why you need neutral, or backing it up a few feet to release the pressure.
 

pjtoledo

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ignore the toothbrush & bolt. they are keeping things from rolling away.
 

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