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Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase!

fixbroke

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TL;DR: rear axle locker light is flashing. Jeep dealer refuses to warranty it due to 4.88s. Problem seems to be locker sensor which is not available for purchase.

So here's the poop:

At around 2000 odo miles, I personally swapped some 4.88s into my new Gladiator Rubicon. It wasn't my first time tearing into diffs and I'm confident in the work. It took a bunch of shimming attempts, but I got a really nice wear pattern that I'm happy with. It ran hot, but I spoke with some experts who said that it was nothing to worry about and not abnormal. I've changed gear oil a few times and the teeth all look nice and happy inside without any excess sludge or shavings in the oil.

6000 miles later, I noticed on a long highway trip that my rear locker light was solidly on. I thought it was strange, but I turned the lockers off and kept going.

1000ish miles after that, the same thing happened on a highway trip while climbing a long hill. This time, however, the light wouldn't go out - it would only flash. It's now stuck this way. I've verified the locker works as normal (on when the light is solidly on, off when it's flashing).

I read a few stories of similar problems, with the warranty resolution being a whole new axle. With my 4.88s, I didn't relish the thought of having to re-gear a new axle but I brought it into my local dealer to see what could be done. As soon as they noticed the "aftermarket gears", they refused to do any warranty work on the axle. This was not entirely unexpected. No worries - I'm a mechatronics engineer, so I thought I'd open it up and do the troubleshooting myself.

The problem seems to be with the sensor that tells the Jeep when the locker is released. This guy, pictured below (pic shamelessly stolen from chevymitchell's excellent DIY 4.88 thread ):
Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! 1594595805862

When the locker is released (as pictured) a magnet slides into the sensor, telling the Jeep that the locker isn't engaged any more. I thought I'd found the smoking gun when the internal wire connector for the sensor turned out to be full of gear oil (the seal had evidently failed), but a thorough cleaning hasn't changed the function. That isn't to say that the oil hasn't gotten inside the sensor housing and ruined something, though.

I tried wiggling everything and I tried running magnets over the sensor, but the Jeep refuses to believe the locker is released.

There are basically two types of magnetic sensors: reed switches and hall effect sensors. This one is likely a hall effect sensor since reed switches aren't typically used in high-vibration environments like an axle housing. It has three pins on the sensor but only two of them are in use, so this tells me that it's a two-pin hall effect sensor that responds to magnetic fields with a change in current. To fully rule out the reed switch I checked resistance between the two active pins while running a magnet over the sensor and there was no change in resistance.

I checked the supply voltage at the sensor connector (6.5 volts), and bench tested the sensor at that voltage to see if I could induce any changes in current. No matter how large a magnet and no matter the polarity, no change to the current. I think the sensor is a dud. Perhaps it didn't like the prolonged heat, or perhaps it got gear oil inside. All I know is I can't get it to react to magnetic fields.

No problem, I'll just buy a replacement - right? Nope.

It turns out that the reason for the full-axle-replacement warranty work that others have received is because Jeep does not sell any axle parts (except for bearings and gears) for the Advantek 44. Bad sensor? Replace the whole axle, complete with housing. Seems pretty ridiculous for a $5 part! FCA part number 10031393, not available.

At this point I have few options. I could pester @JeepCares for help, though the answer there is almost always to see your dealer. I could pester Dana to see if they will sell me the part, but in my experience they refuse to deal with end-users. Lastly, I could bust open the sensor and make a last-ditch effort to fix it, but I'm guessing that any failures inside won't be fixable unless it's a simple broken solder joint.

Anyone have any thoughts or advice for me? (and no, putting a piece of electrical tape over the blinking locker light isn't an option! :giggle:)
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nerubi

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My advice - don't change parts of the factory delivered system and expect the warranty to cover what you could of damaged.. There's a saying in business - you open it you own it.

Replace the entire assembly on your dollar not mine.
 
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fixbroke

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My advice - don't change parts of the factory delivered system and expect the warranty to cover what you could of damaged..
As soon as they noticed the "aftermarket gears", they refused to do any warranty work on the axle. This was not entirely unexpected.
 
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fixbroke

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Holy cow, I found it! I don't know if this does me any good, however, since TE is unlikely to sell me one. Maybe I can get a sample.

https://www.te.com/global-en/product-CAT-ATS0010.html

From the datasheet: "Integrated magnetic shield to minimize external magnetic influences"

...which means I might need to find a smaller magnet to test with before I call it faulty, since the magnets I was using were all too large to slide into the magnet channel.
 

Badweissenbier

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Now you have a model and manufacturer I bet you can find it somewhere for sale
 

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WhereRU_A-A-Ron

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Holy cow, I found it! I don't know if this does me any good, however, since TE is unlikely to sell me one. Maybe I can get a sample.

https://www.te.com/global-en/product-CAT-ATS0010.html

From the datasheet: "Integrated magnetic shield to minimize external magnetic influences"

...which means I might need to find a smaller magnet to test with before I call it faulty, since the magnets I was using were all too large to slide into the magnet channel.
Definitely curious to find out (if they'll sell it to you) whether or not this works. Best of luck!
 
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fixbroke

fixbroke

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Update:
I have the sensor apart and the inside is coated in a light layer of gear oil. The failed seal seems to be the culprit.
Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_135342


Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_140125


The oily mess is clearly visible on the inside of the housing cover.

Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_140328


I de-soldered the hall effect chip from the PCB, and it did produce a current-change response to magnetic fields on the bench, so the chip is probably okay. On the other hand, the PCB itself shows conductivity between the different traces, even with all components de-soldered. I think this means that the fine metal particles suspended in the gear oil have shorted the PCB.

Cleaning the PCB with acetone helped somewhat by increasing the resistance, but there is still conductivity. An electrical engineer friend of mine suggested hitting the bare PCB with 100 volts to burn up the short. He's going to give that a try for me and then hopefully the re-soldered, reassembled, and re-sealed sensor will play nice with the Jeep.

Based on this information, it would be a good idea to check your diff lock sensor connectors for oil intrusion whenever you have your diff covers off. If there is oil in the connector, you may end up with this problem. I will be packing my connectors with a boatload of dielectric grease to hopefully keep oil out in the future.
 

2Wheel-Lee

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Did you remove those capacitors before checking continuity? Was there a value indicated on the underside of the capacitor?
 
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2Wheel-Lee

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I can't remember, but can you remove the sensor without having to remove the entire carrier assembly?

When I regeared my axles at about 1,800 miles, the rear sensor was already caked with crud. I can't remember, but I recall checking the backlash before tearing it down, and it was like more than twice what it should have been.
 

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fixbroke

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Yes, thankfully the screw holding the sensor in place can just barely be removed without having to pull the whole carrier.

I didn't bother checking the backlash before re-gearing, but the hall sensor's magnet was definitely caked with crud after breaking in two sets of gears! I gave it a good cleaning, before attempting more drastic fixes, but it did me no good.
 

Toycrusher

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This might not be popular, but try Alibaba. You can find a dozen Chinese companies there that will bid against each other to reverse engineer and duplicate that sensor for you. You might need to buy a hundred units, but it will still probably be way cheaper than a new axle.

The injection molded housing tooling would be ridiculously expensive so just ask for the guts, the circuit board and seal
 

Glamisfan

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Get the Tazer from Z Automotive and their wiring harness that bypasses this sensor but keeps the computer happy. Actually, I think that you only need to buy the wiring harness. I don’t think the Tazer has anything to do with it?
 

Lou_JLU

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Update:
I have the sensor apart and the inside is coated in a light layer of gear oil. The failed seal seems to be the culprit.
Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_140328


Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_140328


The oily mess is clearly visible on the inside of the housing cover.

Jeep Wrangler JL Flashing rear locker light... bad hall effect sensor? Jeep won't warranty, part not available for puchase! IMG_20200714_140328


I de-soldered the hall effect chip from the PCB, and it did produce a current-change response to magnetic fields on the bench, so the chip is probably okay. On the other hand, the PCB itself shows conductivity between the different traces, even with all components de-soldered. I think this means that the fine metal particles suspended in the gear oil have shorted the PCB.

Cleaning the PCB with acetone helped somewhat by increasing the resistance, but there is still conductivity. An electrical engineer friend of mine suggested hitting the bare PCB with 100 volts to burn up the short. He's going to give that a try for me and then hopefully the re-soldered, reassembled, and re-sealed sensor will play nice with the Jeep.

Based on this information, it would be a good idea to check your diff lock sensor connectors for oil intrusion whenever you have your diff covers off. If there is oil in the connector, you may end up with this problem. I will be packing my connectors with a boatload of dielectric grease to hopefully keep oil out in the future.
Did you happen to notice a part number on the hall effect IC?
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