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

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Nope. It assumes the locker is always successful in locking and unlocking. If there's ever a problem, you won't know about it.
I see.. but it does show up on your dash when you r locked?
 

2Wheel-Lee

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I see.. but it does show up on your dash when you r locked?
As mentioned, the light is on when the locker is turned on. Since the sensor is bypassed, there's no confirmation signal that that it is in fact locked.

Just the same, the locker may be stuck on mechanically, but since there's no signal going to the sensor bypass harness, there will be no light on the dash. You'll likely only know that the locker is stuck on when you get to pavement. I've had them stick locked and had to drive on the streets this way....chirp, chirp, chirp....around corners. Have I mentioned in this thread how much I love ARB lockers? (I have them in another vehicle.)

I already know how the conversation will go....So there I am stuck in some rocks, with both locker lights are on. I'll be asking those around me if my wheels appear locked or if one is not spinning. Of course, it wasn't uncommon to still ask this in case an axle shaft or something broke, and we didn't hear it.
 

CaJLMetalHead

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Hey fixbroke.. is it possible for you to get the IC part number? or a photo? or both.. I know you said Google didn't return much.. but I am familiar with electronics and I am good at finding stuff.. and I would like to help reverse engineer this sensor and possibly find a cheap solution to the problem.. Also... can you please take a photo of the other side of the PCB?

Is that hole close to C2 used to secure the PCB against the housing using a metal bolt?.. that hole is clearly Ground .. which is the leftmost pin on that PCB photo.. also.. when you measure the voltage on the other two pins in reference to Ground... what do you get? .. Thanks!
 
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fixbroke

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Hey fixbroke.. is it possible for you to get the IC part number? or a photo? or both.. I know you said Google didn't return much.. but I am familiar with electronics and I am good at finding stuff.. and I would like to help reverse engineer this sensor and possibly find a cheap solution to the problem.. Also... can you please take a photo of the other side of the PCB?

Is that hole close to C2 used to secure the PCB against the housing using a metal bolt?.. that hole is clearly Ground .. which is the leftmost pin on that PCB photo.. also.. when you measure the voltage on the other two pins in reference to Ground... what do you get? .. Thanks!
Sorry, I don't have the busted sensor any more, but here's a pic of the other side of the PCB. The hole is a mounting hole, which uses a melted plastic boss in lieu of a fastener.

IMG_20200714_135342_crop.jpg
 

CaJLMetalHead

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Sorry, I don't have the busted sensor any more, but here's a pic of the other side of the PCB. The hole is a mounting hole, which uses a melted plastic boss in lieu of a fastener.

IMG_20200714_135342_crop.jpg
Ok cool.. thanks... question... which pins are connected .. I see that there only two pins connected... is it the outer ones? Thanks!
 
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Yup, the two outer pins on the housing connector are connected to the Jeep locker harness. Note that these aren't the two outer pins on the hall chip, though.
 

wibornz

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I could send you one if you want to try and repair it.
 

CaJLMetalHead

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Hey fellas.. I removed my ring gear/locker assembly and I disassembled the sensor.. I drew this circuit diagram and did some testing..



1600273907839.png



The operation of this sensor is simple.. it is a Hall Effect Switch operating in current regulation mode... what does it mean? ... when fed with electricity the sensor allows a specific amount of current to circulate when not in the magnetic flux... once in the magnetic flux and when it reaches the threshold it "switches ON" allowing more current to flow.. a very specific value... so this is what I measured..

Not in the magnetic flux (Locker off) = 5.87 ma (milliAmps)
In the magnetic flux (locker engaged) = 14.18 ma (milliAmps)

The way the sensor works in more detail: a positive voltage/current is sent through the "Locker Switch Sense" Pin 2 of the Locker connector (the external connector on the pumpkin) this positive current travels internally on the White cable to Pin 1 on the sensor and the current returns on Pin 3/Blue Cable back to the "Locker Sensor Return" ... the Drive Train Control module measures the current returning from the sensor to determine if the locker is engaged.. So 5.87 milliAmps… Locker not engaged.. 14.18 milliAmps… Locker engaged!!!.. Wohooo!!

Here is a picture of the front of the Hall Effect Switch Chip.. really nothing special.. those numbers "4206" and "9759" in the front most likely indicate the date of manufacturing.. with the 42 on the first row indicating week #42 of the year and the leading "9" on the second row indicating the year as 2019 ... Also, I do not believe this is some sort of mythical.. Obscure, handmade, and individually calibrated sensor. It seems to me like a simple off the shelf Hall Effect sensor. Unfortunately, it has no logo/part number from the manufacturer… if we are willing to look further then we will need to find one with very similar current outputs (5.87ma / 14.18ma) and with the same pinout (depicted on the second photo below)

1600276042615.png



PINOUT

1600278425175.png



Just to avoid confusion since you might be asking yourself about the "Output" pin that seems to be unused since it is not connected in any way to the " Drive Train Control module " .. the way this sensor is configured the current flows from the "Input" to the "Ground" pin.. so effectively the "Ground" pin becomes the output and the "OUTPUT" pin is left unused... this configuration forces the Chip to go into the current regulation mode, this is commonly referred as "2-Wire" configuration (this Chip also works in 3 wire configuration mode... where "Input" pin is supplied with a voltage, Ground pin is connected to Ground .. and the "Output" pin generates a voltage proportional to the magnetic flux, this a simpler way to use the sensor) .. the reason to go with 2-wire configuration is that current sensing is less affected by electromagnetic interference compared to voltage transmission on the cable back to the module.. the tradeoff is that current sensing is more difficult to process .. but hey.. these are $50K rigs... so not a big issue to spend more $$ in module development.

In reality, I believe this is an exercise in futility as I imagine that FCA is going to eventually stock this sensor (hopefully a new version that does not fail prematurely like the current one) ... anyway... it was fun to hack this thing and I hope this helps the community ...

Any questions? please feel free to ask!
 
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