4WD not working

Click · Jan 23, 2016

I have a 95 Mazda B4000 4.0 Bought it used and 4WD never worked. Lights flash upon turning the key then go off. Silly me I went and replaced the Auto hubs to Manual thinking that would do it. It didnt.

So I put a test light down to the motor on the Transfer case and I am getting no power. I followed it up to another connector and still no power.

The 4wd fuses are good.

The relay under the dash is good and clicks in accordance with the ECM behind the radio.

The #28 fuse has no power and according to my manual thats the GEM fuse. Lights, chimes wipers all work.

I have an ABS light on the dash and really other than the airbag light thats all thats work. The dash is dark.

No codes

I could use some direction. Much appreciated.

RonD · Jan 23, 2016

The 2 wires going to the shift motor are the only ones that will have power and ONLY when you hear the Relays click.
The 2 relays in the 4WD module are to assign polarity to the shift motor, +/- or -/+
It is a DC motor so can turn clockwise or counter clockwise depending on polarity of it's 2 wires.

The shift motor has its own fuse in engine fuse box.

The other wires near/on the shift motor housing are "location" wires, these tell the GEM module if the motor is moving and where it is in it's movement.
Basically there is a disc inside with metal "lines" that turns with motor movement and makes and breaks contacts inside.
Lights will Flash if GEM doesn't "see" motor moving, contacts opening and closing in the motor housing.

Brown wire is for an electric clutch inside transfer case.

If relays are clicking then GEM is working.

Most common issue is the shift motor has failed, you can rebuild them.
This is a motor that uses 2 brushes on the rotor, these types of motors are fine(and cheap) if you use them often to keep brush surface and rotor clean and moveable.
Problem in this application is that many don't use the 4WD every month, could be months or years go by before they try it and by that time there is corrosion or brushes are stuck and not making contact.
Once you find the problem and fix it, make it a point to shift into 4high and low then back to 2WD once a month, you do not have to drive it, just shift it so motor stays clean.

Tapping on the motor can get brushes to move and motor may start working, but still needs to be cleaned to be reliable.

Go here: http://www.therangerstation.com/tech_library/transfercasetroubleshooting.htm

Very helpful

Click · Jan 23, 2016

I appreciate your answer Ron...and Im busting out my persuasion mallet as we speak... but I did check the current down there with the key on and was not getting any voltage. Does that put a different spin on things?

RonD · Jan 23, 2016

Click said:
.................. but I did check the current down there with the key on and was not getting any voltage. Does that put a different spin on things?

No voltage will be there unless GEM activates the 4WD module(relays), and it doesn't activate the relays unless you change between the selections, 2WD, 4hi and 4lo.
There would be no voltage at the motor the rest of the time, key on wouldn't matter.
And if motor isn't moving GEM would "see" that and cut power to the motor, so you would have maybe 1 or 2 seconds of power

jeremysdad · Jan 23, 2016

As a workaround, since he has manual hubs, can't he pull the motor and use vice grips to engage the transfer case?

I know it's inconvenient, but it could get him to work...

Click · Jan 23, 2016

Yes a few ratt a tat tatts got it going but only for short spurts. Time to take it off for inspection. Thanks alot!

Click · Jan 23, 2016

RonD said:
No voltage will be there unless GEM activates the 4WD module(relays), and it doesn't activate the relays unless you change between the selections, 2WD, 4hi and 4lo.
There would be no voltage at the motor the rest of the time, key on wouldn't matter.
And if motor isn't moving GEM would "see" that and cut power to the motor, so you would have maybe 1 or 2 seconds of power

New school stuff. Thanks again!

Andy D · Jan 24, 2016

Saturday, in preparation for snow, I slid under the Rat and wired the Vise grips in 4 high. With the hubs locked, I am positively in 4wd. The neat thing is that I'm using a set of needle nose VG . It failed at every other job until I wired it in place of the shift motor.

jeremysdad · Jan 25, 2016

Andy D said:
Saturday, in preparation for snow, I slid under the Rat and wired the Vise grips in 4 high. With the hubs locked, I am positively in 4wd. The neat thing is that I'm using a set of needle nose VG . It failed at every other job until I wired it in place of the shift motor.

Knew I was right, for once in my life. lol

4WD not working

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