fixbroke

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Some of us are now painfully aware that the locker sensors in the new Advantek 44 Rubicon axles are prone to failure. Even more annoyingly, the sensors are not available to purchase outside of a complete new axle assembly. You cannot buy this sensor if/when it fails.

The main failure cause seems to be that gear oil gets into the sensor housing and shorts the PCB with the fine metal particles suspended in the oil. It happens most often on long highway trips on the rear diff, where there is a lot of heat being generated in the gear oil, which in turn thins the oil to the point that it can get past the sketchy seals of the sensor housing.

This will first result in a flashing locker light telling you the axle is in the process of unlocking, even though it's not locked. Lockers will still work for a while, but eventually the flashing light will be replaced by a solid warning with the message "service axle locker system" and the lockers will no longer engage. If your sensor has gotten to this point, it's too late to save it. You can try to get Jeep to warranty the entire axle, but if you've changed your gearing then they will refuse to warranty due to the modifications. Your only option is to buy a Z Locker OEM to bypass the sensor in the affected axle.

This guide explains how to remove your working sensor and fill it with silicone (aka "potting", a common procedure to protect electronic components) to oil-proof the important bits. Note that if you still have stock gearing, this will void your sensor warranty so you may want to wait till the end of your warranty period before doing this. If you've re-geared, I can't recommend enough that you do this before your sensors fail since you don't have warranty protection anyway and you can't buy a replacement sensor. I've been running mine like this for around 1000 miles now and it has been working well.


1. Drain your differential and remove the cover.

2. Remove the locker sensor torx screw. An L-handle torx wrench works well since there's not a lot of clearance from the bearing cap bolt.
IMG_20200807_163921.jpg


3. Remove the sensor. You may need to push the locker ring towards the ring gear to get enough clearance to free the sensor. At this point it's not a bad idea to clean the metal shavings from the magnet that was hidden under the sensor.

4. Disconnect the wiring connector by sliding the red tab back, then pressing on it while you wiggle the connector free.
IMG_20200807_164751.jpg


5. Drill a small hole in the white plastic cap. You can use a much smaller bit than what's pictured, or better yet use a small rotary tool. BE VERY CAREFUL that the drill doesn't pull itself into the PCB inside. Go very slowly, or use a rotary tool that won't pull itself into the hole. Remember that these sensors are unobtainium and you're gonna feel really bad if you break it!
IMG_20200807_164140.jpg


6. Drill another small hole in the pocket on the other side of the sensor. Again, BE VERY CAREFUL not to damage the PCB inside.
IMG_20200807_164157.jpg


7. Use a small tube of RTV silicone to push silicone through the bottom hole until it completely fills the sensor and exits the top hole. I used red high-temp RTV since I had it on hand, but any kind will do so long as it's not electrically conductive. Do not use the copper stuff!

8. Allow the silicone to cure, then trim off any excess with a knife.
IMG_20200807_164411.jpg
IMG_20200807_164418.jpg


9. As an additional precaution, I filled my connector with dielectric grease since I suspect that is a major path for oil to enter the housing. EDIT: there's some contention as to whether dielectric grease is suitable for sealing connectors. You may wish to skip this step.
IMG_20200807_164546.jpg


10. Reinstall the sensor. I recommend using some blue threadlocker on the torx screw.

11. Reinstall the diff cover and refill your diff oil. You're done! Your sensor should now be potted and oil-proofed.





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mgroeger

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Some of us are now painfully aware that the locker sensors in the new Advantek 44 Rubicon axles are prone to failure. Even more annoyingly, the sensors are not available to purchase outside of a complete new axle assembly.

The main failure cause seems to be that gear oil gets into the sensor housing and shorts the PCB with the fine metal particles suspended in the gear oil. It happens most often on long highway trips on the rear diff, where there is a lot of heat being generated in the gear oil, which thins it out to the point that it can get past the poor sealing and into the sensor housing.

This will first result in a flashing locker light telling you the axle is in the process of unlocking, even though it's not locked. Lockers will still work for a while, but eventually the flashing light will be replaced by a solid warning with the message "service axle locker system" and the lockers will no longer engage. If your sensor has gotten to this point, it's too late to save it. You can try to get Jeep to warranty the entire axle, but if you've changed your gearing then they will refuse to warranty due to the modifications. Your only option is to buy a Z Locker OEM to bypass the sensor in the affected axle.

This guide explains how to remove your working sensor and fill it with silicone (aka "potting", a common procedure to protect electronic components) to oil-proof the important bits. Note that if you still have stock gearing, this will void your sensor warranty so you may want to wait till the end of your warranty period before doing this. If you've re-geared, I can't recommend enough that you do this before your sensors fail since you don't have warranty protection anyway. I've been running mine like this for around 1000 miles now and it has been working well.

1. Drain your differential and remove the cover.

2. Remove the locker sensor torx screw. An L-handle torx wrench works well since there's not a lot of clearance from the bearing cap bolt.
IMG_20200807_163921.jpg


3. Remove the sensor. You may need to push the locker ring towards the ring gear to get enough clearance to free the sensor. At this point it's not a bad idea to clean the metal shavings from the magnet that was hidden under the sensor.

4. Disconnect the wiring connector by sliding the red tab back, then pressing on it while you wiggle the connector free.
IMG_20200807_164751.jpg


5. Drill a small hole in the white plastic cap. You can use a much smaller bit than what's pictured, or better yet use a small rotary tool. BE VERY CAREFUL that the drill doesn't pull itself into the PCB inside. Go very slowly, or use a rotary tool that won't pull itself into the hole. Remember that these sensors are unobtainium and you're gonna feel really bad if you break it!
IMG_20200807_164140.jpg


6. Drill another small hole in the pocket on the other side of the sensor. Again, BE VERY CAREFUL not to damage the PCB inside.
IMG_20200807_164157.jpg


7. Use a small tube of RTV silicone to push silicone through the bottom hole until it completely fills the sensor and exits the top hole. I used red high-temp RTV since I had it on hand, but any kind will do so long as it's not electrically conductive. Do not use the copper stuff!

8. Allow the silicone to cure, then trim off any excess with a knife.
IMG_20200807_164411.jpg
IMG_20200807_164418.jpg


9. As an additional precaution, I filled my connector with dielectric grease since I suspect that is a major path for oil to enter the housing.
IMG_20200807_164546.jpg


10. Reinstall the sensor. I recommend using some blue threadlocker on the torx screw.

11. Reinstall the diff cover and refill your diff oil. You're done! Your sensor should now be potted and oil-proofed.
Nice write up! My sensor went bad so I swapped it with a good one and took the old one apart. I was able to pop off the top of the bad one to clean it out but haven't tested it yet.
One thing I did do on the new one is a put silicon all around the edge of the clear plastic top. That way the gear oil doesn't even make it in. The only thing I can see with your idea is if there is an air pocket in there any gear oil that makes it past the cover can still get in it. To be completely thorough a bead of silicon around the lip will seal it off.
 
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fixbroke

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One thing I did do on the new one is a put silicon all around the edge of the clear plastic top. That way the gear oil doesn't even make it in. The only thing I can see with your idea is if there is an air pocket in there any gear oil that makes it past the cover can still get in it. To be completely thorough a bead of silicon around the lip will seal it off.
It might not be a bad idea to combine that with the internal potting. I know that @wibornz tried the edge-seal method and still ended up getting oil in his new sensor, though, so I think potting will be more effective.

I suspect the main entry point is through the connector rather than the plastic seam. It's likely that the third, unused pin on the 3-pin connector is letting oil into the connector and then into the housing, hence my liberal application of dielectric grease.
 

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FYI, "Dielectric grease, or tune-up grease, is a silicone-based grease that repels moisture and protects electrical connections against corrosion. ... The grease does not conduct electricity, so it shouldn't be applied directly to the mating surfaces (pins and sockets) of an electrical connection."
Search conductive grease for electrical connectors
 
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fixbroke

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FYI, "Dielectric grease, or tune-up grease, is a silicone-based grease that repels moisture and protects electrical connections against corrosion. ... The grease does not conduct electricity, so it shouldn't be applied directly to the mating surfaces (pins and sockets) of an electrical connection."
Search conductive grease for electrical connectors
Conductive grease seems like it would be a bad idea for a multi-pin connector. My understanding is that as mating contacts slide against one another, the dielectric grease is pushed away from the contact area and the mating contacts have no additional resistance. Usually it's packed into connectors as a corrosion inhibitor, and its dielectric nature prevents conductivity between adjacent pins.
 

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Has anyone actually broken a locker or have these been the failures ultimately?
 

mgroeger

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Has anyone actually broken a locker or have these been the failures ultimately?
The failure is the second switch failing by getting gear oil in it. No one has broken their locker.
 
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fixbroke

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Pop the lid off and just fill it that way?
You might have a hard time getting the silicone distributed to both sides of the board. Also, popping the lid off is a lot harder than drilling a couple of holes.
 

mgroeger

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You might have a hard time getting the silicone distributed to both sides of the board. Also, popping the lid off is a lot harder than drilling a couple of holes.
My lid came off easy since it had already started to separate.
 

four low

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Great write up, thank you. If you have a FAILED unit, could you drill the 2 holes, flush it with electric contact cleaner, dry thoroughly, and do the Potting ? Once the metal particles are removed, it should work ?
Also, could reassembling the electrical connector with the same silicone seal better than grease, which might not seal out diff oil, under heat over time ?
Thanks in advance
 

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How did you get the new one? They won’t sell the sensors.
We put factory Rubi axles on my wife's Sahara which means they come with that sensor installed. Since she is using them in an after market configuration, i.e. she doesn't use factory locker control switches, she doesn't need that sensor so I harvested it our of her axle.
 
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fixbroke

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My lid came off easy since it had already started to separate.
Interesting. Mine was a pain in the butt to open up and it broke in the process. This might mean there are some sensors that leak through the connector while others leak through the lid seam.

Great write up, thank you. If you have a FAILED unit, could you drill the 2 holes, flush it with electric contact cleaner, dry thoroughly, and do the Potting ? Once the metal particles are removed, it should work ?
Also, could reassembling the electrical connector with the same silicone seal better than grease, which might not seal out diff oil, under heat over time ?
Thanks in advance
I pulled a failed sensor completely apart and cleaned it with contact cleaner, but the contamination seemed to permeate the PCB. You can easily tell by checking the resistance between the two outer pins on the sensor - if there's any conductivity at all, the sensor is contaminated.

Here's something to try if you have a failed sensor:
An electrical engineer friend of mine tried to salvage my board by de-soldering all the components and running high voltage to the contacts, which was successful in burning up the contamination (ZAP! spark!). Unfortunately the sensor wouldn't work after it was re-soldered, though - I'm not exactly sure why. The PCB checked out okay afterwards, but I might have cooked the sensor while soldering it.
It's also a very simple PCB, so it wouldn't take much to reverse engineer it and have a batch made overseas for around five bucks ( https://easyeda.com/ ). It's the hall sensor itself that is proprietary and non-replaceable.
 

DaveC

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We put factory Rubi axles on my wife's Sahara which means they come with that sensor installed. Since she is using them in an after market configuration, i.e. she doesn't use factory locker control switches, she doesn't need that sensor so I harvested it our of her axle.
I'm getting ready to put some take off axles in my sport. I don't have to worry about this sensor right?
 

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