Rubi owners, keep your locker sensors from failing! How to pot your sensors

[fixbroke]

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.

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.

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!

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.

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.

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, but if you're feeling curious then read on in this thread for a discussion of its intended use.

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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[wannajeep]

Great write-up and pics, thank you.

Do you do this for the front as well?

 

[fixbroke]

Do you do this for the front as well?

I haven't heard of any fronts failing, but I'll probably do it next time I have the front diff cover off.
It's the same sensor, but the front sees so much less use and at lower speeds so I don't think the oil gets hot and thin enough to breach the sensor housing. Or perhaps it's just a matter of time and we'll see those fail in the years ahead.

 

[ShadowsPapa]

Aren't you concerned that the silicon will eventually fail after the constant oil exposure?
I've seen a lot of it used on differential covers, axle seal areas and such over the years and, well, it's good to seal those but I'd be tempted to use an epoxy or a true potting material.
I've made new voltage regulator circuits and will be using true potting material to seal them into cases I'll gut and recycle so people can have the correct style and look but with new electronics inside.
Might try "right-stuff". It has held up better on intake manifolds that cover the valley area and have constant exposure to hot oil.
Still - would epoxy work?

Just a tip for onlookers- DIelectric is used to seal things like plug wire boots - if you get it on the conductors, it's an insulator.
We learned to never use it on tail light bulb sockets. Big discussion on the forum I operate when people used it on bulbs and then complained they had just as many tail light issues - they wiped off the dielectric grease and got connection back.
I use "No-ox" or whatever it's called.

I know this will get me flamed but just trying to insert personal experiences and explain that dielectric could cause connection issues in low voltage, low current cases.
NOT trying to insult anyone or say "no, don't do this!", just passing along experience from over the years.

 

[fixbroke]

Aren't you concerned that the silicon will eventually fail after the constant oil exposure?

It's my understanding that RTV gasket maker is highly resistant to oil. Regular silicone, not so much. It might not be the ideal potting material but it was on hand and oil resistant. I did a little bit of research into oil-resistant potting compounds but didn't come up with anything satisfactory, so RTV got the job.

Just a tip for onlookers- DIelectric is used to seal things like plug wire boots - if you get it on the conductors, it's an insulator.
We learned to never use it on tail light bulb sockets. Big discussion on the forum I operate when people used it on bulbs and then complained they had just as many tail light issues - they wiped off the dielectric grease and got connection back.
I use "No-ox" or whatever it's called.

Someone on the JL forum said something similar. It's always been my understanding that after the contacts have scraped each other during connector installation, whatever layer of dielectric grease remains on the contact is so thin that the added resistance is negligible. Your experience plus the other gentleman's input have me reconsidering that. Perhaps the way I learned to use dielectric grease is wrong.

 

[WhatExit?]

Do I understand this correctly that you're advocating modifying the locker sensor on a Gladiator that's under warranty to avoid having a problem (sensor failure) that will be replaced under warranty?

 

[WhatExit?]

You may want to look at this:
https://www.jeepgladiatorforum.com/...r-system-lockers-wont-engage-disengage.33037/

 

[MrFahrenheit]

@WhatExit? , just an FYI that he mentioned both concerns you have in his original post:

Do I understand this correctly that you're advocating modifying the locker sensor on a Gladiator that's under warranty to avoid having a problem (sensor failure) that will be replaced under warranty?

From his original post:

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

You may want to look at this:
https://www.jeepgladiatorforum.com/...r-system-lockers-wont-engage-disengage.33037/

From his original post:

Your only option is to buy a Z Locker OEM to bypass the sensor in the affected axle.

 

[ShadowsPapa]

It's my understanding that RTV gasket maker is highly resistant to oil. Regular silicone, not so much. It might not be the ideal potting material but it was on hand and oil resistant. I did a little bit of research into oil-resistant potting compounds but didn't come up with anything satisfactory, so RTV got the job.



Someone on the JL forum said something similar. It's always been my understanding that after the contacts have scraped each other during connector installation, whatever layer of dielectric grease remains on the contact is so thin that the added resistance is negligible. Your experience plus the other gentleman's input have me reconsidering that. Perhaps the way I learned to use dielectric grease is wrong.

I have used black, gray, red, etc. for years and all eventually fail - with some exceptions....... My 73 intake is already leaking on the front where it covers the valley - the RTV failed and got really slimy. I reset that intake 2 years ago. It seems to do well in extremely thin layers like sealing around the water ports where it's squeezed out into a layer about .002" or so, but at the ends where it's about .175" to .25" it fails. (tip for onlookers - it's crap on thermostat housings with constant antifreeze exposure. Anaerobic sealers are best there)
Anyway, it would be really interesting to see this over time - say, how has it done in a year?
A good case study going on here!!
And frankly, I'm surprised they don't seal that baby from the get-go anyhow! Really? A PC board exposed to hot oil?

Ah, dielectric grease - my boss in the 90s used to call the internet the misinformation stupid highway.... and the proof that bad info travels fast I have a GREAT example of -
In the mid 1990s I put up web pages about the processes I used to remove rust - electrolysis. I did tons of research - I left no stone unturned, used it a few times and then did a write-up on it. However, I used bad info in one area related to hydrogen, the Hindenburg, etc. - I got new, better info from a NASA engineer on the subject of the Hindenburg. But before I could change my text, I was noticing other pages springing up about this neat way to derust parts for restoration of cars, antique engines (my page was related to that) and other stuff. And guess what - it was mostly my text rearranged a bit - and, included my mistake! I found page after page after page out there, my info,, bad and all, including a couple TYPOs I had - teh instead of the (ADHD does that to you, brain goes 100 times faster than fingers so you screw up simple words when typing)
It was soo funny! I thought now there's a great way to make 100 mistakes at once - put it on the web and in weeks others have copied it, BAD info and all, typos and misspelled words included.
And that's the deal about dielectric. It's an insulator that gained popularity in sealing almost anything electric while originally it was used in the spark plug boots of HEI systems. GM recommended it because it sealed the HIGH VOLTAGE from leaking out of the plug boots to ground and made the plug boots a ton easier to get back off later (sometimes we ripped them getting them off because of the extended tune-up intervals electronic ignition systems allowed)
Suddenly you see it being sold and used on almost everything.
Ideally it should be "scraped off" of a tight connection - but over time, heat, vibrations and so on, it gets worked in between the conductors in some cases. All? No - there's so much success that the info about it being a dielectric insulator just doesn't get around. The failure rate is low so no one is out there screaming "Don't do that!".
I'd only suggest that - be aware, and., make sure the connections are TIGHT mechanically.

Two ideas come to mind while typing - liquid tape - I use it a lot on wiring and hangers I use in my plating tanks, and a tape I've used on some other connections that works by adhering to itself - there's no adhesive involved. When wrapped tightly around itself, it bonds to itself. It's like a heat shrink for wires you can't slide anything onto. BUT - it may not hold up to oil exposure!
Liquid tape may - it holds up well to acids in the plating baths and caustics I use for cleaning.

Are your ideas an end-all fix? Will they hold up? It will be interesting to see. The ideas and what's happening here is interesting research even if it doesn't hold up long-term.
And if it does - COOL and congratulations!

I still can't believe they didn't SEAL that and the connections - heck, other connections are environmentally sealed and most aren't exposed to extremes.

 

[Factoid]

You really want a conformal coating like we used on sensitive weapons systems PCBs in the military. To answer the question, an epoxy is a better solution.

https://www.paryleneconformalcoating.com/conformal-coating/#

 

[WhatExit?]

@WhatExit? , just an FYI that he mentioned both concerns you have in his original post:



From his original post:




From his original post:

THANKS! Sorry I missed that - I was so involved in reading about the process steps, drilling and filling, that I missed those 2 points.

 

[ShadowsPapa]

You really want a conformal coating like we used on sensitive weapons systems PCBs in the military. To answer the question, an epoxy is a better solution.

https://www.paryleneconformalcoating.com/conformal-coating/#

Potting materials are available all over - Mouser, Allied, Digikey, many places. Good stuff isn't cheap, but neither is taking apart a differential and getting to an electronic part to replace - or worse, having to replace the whole assembly due to lack of individual part!

I'm going to pot these in aluminum housings when I get the thermistor portion figured out (how to increase regulated voltage (about .4 volts) as ambient temperature drops)
But the potting must be heat conducting to keep the components cool - and allow them to sense the ambient air temp around the regulator.

 

[fixbroke]

I have used black, gray, red, etc. for years and all eventually fail - with some exceptions....... My 73 intake is already leaking on the front where it covers the valley - the RTV failed and got really slimy. I reset that intake 2 years ago. It seems to do well in extremely thin layers like sealing around the water ports where it's squeezed out into a layer about .002" or so, but at the ends where it's about .175" to .25" it fails. (tip for onlookers - it's crap on thermostat housings with constant antifreeze exposure. Anaerobic sealers are best there)

I wonder if your intake RTV failed due to fuel exposure. I can confirm that it definitely doesn't like fuel. I'm not saying it is invulnerable to oil, but the stuff is sold specifically as an oil-resistant sealant.

Perhaps there's a better potting compound, but the cursory research I conducted didn't show "oil resistance" as a common potting compound trait. Epoxy would probably hold up best.

I'd be very surprised if the potting fails due to oil exposure. There's a thick layer separating the components from the oil, so it would have to permeate well into the cured material. Being that it's only splashed with oil and not under pressure, I'm going to be bold and say that even if the exposed RTV begins to degrade, it will still prevent oil from reaching the potted electronics.

I still can't believe they didn't SEAL that and the connections - heck, other connections are environmentally sealed and most aren't exposed to extremes.

They tried! The connector does have an internal boot, but I don't think they sealed the missing pin location. My connector was full of gear oil. The seam on the plastic housing is also supposed to be sealed, but perhaps that bonding agent is another that doesn't like gear oil.

Re the dielectric grease - I'll update my instructions. Using it in this sensor should be safe, however, since it functions as a current source and shouldn't be affected by any added resistance. Voltage- and resistance-based sensors, on the other hand, would be subject to erroneous readings with any added resistance.

 

[ShadowsPapa]

I wonder if your intake RTV failed due to fuel exposure. I can confirm that it definitely doesn't like fuel. I'm not saying it is invulnerable to oil, but the stuff is sold specifically as an oil-resistant sealant.

Perhaps there's a better potting compound, but the cursory research I conducted didn't show "oil resistance" as a common potting compound trait. Epoxy would probably hold up best.

I'd be very surprised if the potting fails due to oil exposure. There's a thick layer separating the components from the oil, so it would have to permeate well into the cured material. Being that it's only splashed with oil and not under pressure, I'm going to be bold and say that even if the exposed RTV begins to degrade, it will still prevent oil from reaching the potted electronics.



They tried! The connector does have an internal boot, but I don't think they sealed the missing pin location. My connector was full of gear oil. The seam on the plastic housing is also supposed to be sealed, but perhaps that bonding agent is another that doesn't like gear oil.

Re the dielectric grease - I'll update my instructions. Using it in this sensor should be safe, however, since it functions as a current source and shouldn't be affected by any added resistance. Voltage- and resistance-based sensors, on the other hand, would be subject to erroneous readings with any added resistance.

With the valley cover type intake AMC used, there's no fuel there, strictly heat and oil.
That's one reason I won't use it around the intake ports.
These intakes cover the valley between the heads, where the lifters are and the end seals are exposed only to oil.

Either way, you are at a minimum protecting things for a while and if it holds up, for a longer while until you no longer care (unless you keep the JT for life, that is)

Fingers crossed here...........

 

[Cdemarac]

I’m still working on pricing but it looks like I have a line on replace sensors. Still trying to work out the details

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