Post-mortem/diagnosis of failed encoder motor sensor

[wagnewvt]

Bravada NVG 126 Transfer Case felt like it was always engaging all 4 wheels, binding in low-speed turns, etc.

Long story short, see related thread http://forums.trailvoy.com/showthread.php?t=52279, it was a bad encoder motor sensor.

Wanted to show pictures, but couldn't upload for some reason.

Here is the text version of the resistance readings as it is rotated. The first picture was supposed to show an open (greater than 30KOhm) reading across the middle and right pins with the notch at roughly the 7 o'clock orientation using the pins as a 12 o'clock reference:

Spinning the notch counter-clockwise and stopping every 90 degrees, the readings across the middle and right pins are:
Notch Reading
7 o'clock open
9 o'clock 1.26K
12 1.70K
3 2.41K
6 2.43K

The same sequence, but across the middle and left pin:
6 o'clock 1.25K
7 o'clock open
9 2.47K
12 2.07K
3 1.26K

If someone could test a brand new unit using the same sequence, we now have an easy way to test an encoder motor sensor.

[If anyone wants to share the trick with me on how to upload pictures, I've got 'em, but I couldn't get one 3MB image to upload - and it was within the size and dimension limits.]

[the roadie]

Pic didn't show up. Are you hosting it elsewhere and using the Image tags?

[sonomacrewcab]

we had the same problem with our 02 bravada

[wagnewvt]

Resized pictures to 800x600 per Roadie's advice. Success!

When I used the word 'notch', I was describing the round protrusion into the center of the sensor.

Note the numbers on the bottom: "02287". I suspect it is a manufacturing date code, corresponding to the 287th day of 2002.

If anyone else has one of these sensors, I'd be interested to compare the numbers on the bottom.

[guano2]

So I geuss this goes on ,or in the en. motor?... Is this what fails, requiring whole motor replacement?:hissy: (different for diff. 4wl systems:undecided)..... & thanks wagnewvt for addressing this issue.:thumbsup:

[the roadie]

It stacks in line with the encoder motor - #29 in this drawing. Often, the encoder motor goes bad mechanically or in its gear train. Not clear whether the cheaper sensor is the root cause of more failures than the motor or not. At least it's available separately, but an entire encoder motor replacement is often cheaper if you get it off Ebay.

http://www.compnine.com/largeimg/030904TX04-028.gif

[vinman]

I really don't mean to get :offtopic: or anything but...

and this might be a dumb question, but would the encoder motor (if bad) also cause the awd to not engage or not engage as "quickly" as it should?..this past winter i've gotten stuck trying to back out of my parking space at work (snow drift that was just below the rear bumper and on completely level ground)

and on cold days i would hear a rapid tick that seemed like it was coming from under the cabin (maybe x-fer case)

[the roadie]

...would the encoder motor (if bad) also cause the awd to not engage or not engage as "quickly" as it should?...Certainly would. The encoder motor, like most actuators, has a gear train to reduce the RPM and amplify the torque coming from a small motor. When cold, the grease on the gears will congeal and slow down the engagement. Not much of an issue for selectable 4WD models, since we hardly ever choose A4WD mode if conditions are such that 4HI is useful. But for you, it might make all the difference.

Have you changed the transfer case fluid every 50K as the Owner's Manual recommends?

[vinman]

i haven't changed the x-fer case or even the rear-end fluids..and i know its due (just barely hit 100k). maybe that can solve my issue..at least i hope

[wagnewvt]

No fluid change until 100K? Sounds like grounds for impeachment of a Chapter President!:D

[edfaunce1]

It stacks in line with the encoder motor - #29 in this drawing. Often, the encoder motor goes bad mechanically or in its gear train. Not clear whether the cheaper sensor is the root cause of more failures than the motor or not. At least it's available separately, but an entire encoder motor replacement is often cheaper if you get it off Ebay.

http://www.compnine.com/largeimg/030904TX04-028.gif

The exploded view you show here is different than the one I got off the DYI site. The one I have just shows the controller motor going into the back of the case without this sensor in between. My 2002 Brav is having 4wd all the time issues. I changed transfer case fluid today, and my buddy took the motor off the actuator housing to check it. It runs great both directions. Looking for the sensor now, but before I take the whole thing off I need to find it. Was there two different models of sensor? Or did I get some bad paperwork?