New takeoff locker - I'm missing something

[Brian_B]

The tl;dr up front is I have a locker and I can't get it to work.

I bought a take off rear end back around Christmas so I could add a rear locker to my 4.46. Got it installed right after New Years.

Not having factory lockers, I ran the wiring to a relay. When I first installed it - it clicked and locked once. I unhooked it to clean up the wiring, and when I reconnected it, it blew fuses. Going down that path of troubleshooting, I found the coil itself was shorted - 0 ohms at the pigtail coming directly off the coil.

So, I did some research, a lot of it is around here. I ordered new parts:

It took a while for the parts to get in, the carrier bearing was backordered until just this week. Today was the first day I had to get into it and replace the coil. It sounded easy - just pull the axles back, pop the carrier out, pull the right carrier bearing, and swap the coil.

Here's the carrier, this is after I got it out with the old coil in it. It looks identical when I got it put back together.

Just for the sake of completeness, here's a picture of the pinon with the carrier pulled.

Apart from the carrier bearing being an absolute pain to get off, there wasn't much to it. Put it all back together - doesn't work still.

I don't blow fuses anymore, so there's that. But the coil doesn't engage. No click, and doesn't lock - checked by jacking up one tire and spinning it.

Brand new coil out of the box was 4 ohms. Installed, checking resistance all the way back to the relay with everything plugged in, I'm getting 4.2 ohms. So that looks good. I'm getting 12V at the outer plug, and on the internal side of the plug - so that looks good. Polarity matches the Red (+) on the coil wiring.

When I turn on the coil, with a clamp on I can see current spike a bit and then settle down to around 4 amps. Swapped relays just in case it was something goofy with that.

Pretty sure everything went back the way it came apart - there wasn't exactly a lot to it - a small plate underneath the coil, the coil, and the carrier bearing. The little catch on the carrier housing that hitches a welded pin on the coil.

I can't even really think of anything else to check. Any ideas? Maybe it's working and I just am not testing it right? I'm stumped.

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[Brian_B]

So I had a good suggestion to run a new wire straight back to the battery. No difference, at least going through the outer connector. The connector I had bought (P/N WPT-829) to use was a bit loose, and I did see it had one of the internal pins on the harness on the diff housing a bit bent and thought - ah ha! But no, fixed all of that, could still see the coil all the way through to the battery (4.2 Ohms), and electrically I can't find anything wrong at all.

So I called around my area to some rear end shops. The first three all said some combination of "That's too new for me", "I don't know anything about electric lockers" and/or "Just take it to the dealer".

Yeah, not going to my dealer though. (Sorry to all you who work at dealers on here, you are all great I'm sure, but my local dealer I am not fond of)

The 4th shop agreed to put it up on the rack, pop the cover and see what's going on. I don't know enough about the mechanicals to know what it's supposed to look like, other than I should be hearing a click and the axle should lock. So I take it in next week to see what we can see.

 

[BroncoBoy22]

Paging @BigMeatsBronco @Bmadda

these guys are two of the biggest modders on here and might be able to help

 

[Bmadda]

Paging @BigMeatsBronco @Bmadda

these guys are two of the biggest modders on here and might be able to help

I was just reading it! One simple test would be to turn it on w/the cover removed and see if a screwdriver or something ferrous sticks to the coil. Thats its only job, so if its generating magnetism then there is a mechanical issue in the diff, and would have to come back out of the housing to fix likely. Could be a little piece of the old coil that got jammed in it etc

 

[BigMeatsBronco]

I'm wondering why you're blowing fuses in the first place? I would follow your wiring through again and make sure you have that absolutely correct.

 

[BigMeatsBronco]

I'm guessing you'll have to rotate one of the axle shafts while you're doing the check to see if it's working, once the voltage is applied and the magnet applies pressure to the spline/dog portion that slides and locks the carrier, one of the axles would like we need to be rotated just slightly to get the dogs to engage or splines to engage fully and then you might hear a click and you might not but you should see the device move slightly once the splines and are aligned

 

[Dialtone]

This thread is why I come here. Good people helping the lost.

 

[Salt Shaker]

It has been years since I pulled a diff apart and played with gears. That being said, couldn't you jack up the axle on both sides a spin the tires in neutral to see if it is engaged?

 

[Fasteddy]

From reading the diagnostics info from the shop manual it appears that ELD voltage range is 4.71 to 5.29 volts, and high current DTC is set at 4.6 amps or greater for over 50 ms.
Given this info and the results of applying 12 volts directly to the coil, current / inductive spike it would appear that you need to have more then just a relay / apply voltage to be successful.

The AWD module most likely uses a PWM signal driving a power MOSFET to drive the coil.
The AWD module diagnostic section mentions the ability to detect over temp condition at the ELD, this would be done via use of a 'one wire' bus type of communication over the power circuit.

Just my take on it, but your mod may be a bit more complex to get working using the OEM type coil.

 

[Brian_B]

I'm wondering why you're blowing fuses in the first place? I would follow your wiring through again and make sure you have that absolutely correct.

Thanks. The first coil I had shorted out - 0 ohms on the coil. That was what was blowing fuses. If my wiring caused the short - I suppose that’s possible (part of the reason I’ve been checking out all the connectors) - but physically the coil looks fine (or it did before I mangled it cutting the carrier bearing out), and apart from going with way too much voltage I can’t think of a way to short it electrically, but stranger things have happened.

That said I replaced that coil and I can’t answer why the second isn’t working - it isn’t blowing fuses.

I was incorrect about it drawing current though - I was measuring the wrong line under the hood. The coil isn’t drawing anything - 0 A - but it shows proper resistance. Verified this going straight to the coil with a separate battery - taking all my wiring and electrical out of the equation.

So I am thinking it’s another bad part - but I’m swallowing my pride and taking it into a 4W shop Monday. I don’t have all the tools to do the carrier bearings right and don’t want to chance it on another one if I have to pull that coil back out again.

 

[Brian_B]

Just my take on it, but your mod may be a bit more complex to get working using the OEM type coil.

Maybe. But plenty of people run it from
12v and the Ford Performance axles just use a relay when adding them to a non-ELD equipped Bronco. So you are not incorrect and maybe that is my problem but seems it should still work regardless. Hopefully I’ll find out something on Monday when I take it in.

 

[Brian_B]

It has been years since I pulled a diff apart and played with gears. That being said, couldn't you jack up the axle on both sides a spin the tires in neutral to see if it is engaged?

Yup. That would work. I had only jacked up one side but as BMB said, maybe that wasn’t enough movement to engage.

 

[Fasteddy]

Maybe. But plenty of people run it from
12v and the Ford Performance axles just use a relay when adding them to a non-ELD equipped Bronco. So you are not incorrect and maybe that is my problem but seems it should still work regardless. Hopefully I’ll find out something on Monday when I take it in.

I wonder if the Ford Performance coil is the same part number as the OEM???

 

[Bmadda]

I wonder if the Ford Performance coil is the same part number as the OEM???

Mine are oe and they do work off 12v. The computer applies 12v for 30 sec, then drops the voltage to 7-8v for reasons no one is quite sure (might be residual magnetism?). Guys have tested by leaving them hooked to a battery overnight on a bench and they work fine. I can't find the thread where we tested this, but it was a similar situation where a guy was upgrading

 

[Felix808]

Mine are oe and they do work off 12v. The computer applies 12v for 30 sec, then drops the voltage to 7-8v for reasons no one is quite sure (might be residual magnetism?). Guys have tested by leaving them hooked to a battery overnight on a bench and they work fine. I can't find the thread where we tested this, but it was a similar situation where a guy was upgrading

My guess it drops voltage for efficiency reason $.02

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