H3 Diff Lock not working

[OmarOHelmy]

My rear axle diff lock has stopped working, when I press the button while in 4Lo, the button flashes then turns off... The display also shows a message: "SERV 4WD" The diff lock button also flashes everytime I start the engine.

I checked under the car and there was a cable running towards the rear axle, it was rubbing against the drive shaft, the wire got bare and may have short circuited, so I cut it, cleaned the connection and sealed with electric tape.

I checked the fuse box, found a blown fuse, replaced it.

But the diff lock still does not work


Any ideas what could be the problem?

Thanks

 

[alrock]

Check the fuse - did it blow again?

 

[Hunner]

Check the wire at the diff for voltage.

 

[rascole]

Are you stopped or slowly moving when trying to engage the locker?

 

[deserth3]

Make sure your buttons are not sticking in. I usually tap the dash to make sure.
You must be going slower than 2mph to switch into 4low. And I think you need to be in neutral.

Sent from my MotoG3 using Tapatalk

 

[4speedfunk]

And preferably rolling. The Eaton needs one revolution to fully engage.

 

[OmarOHelmy]

Hi Hunner,
I checked the wire under the car, yes one of the wires have been cut again, came into contact with the U-joint. So I'm going to try and connect it together. But I wanted to ask you, what do you mean by checking the wire for voltage? I have a multimeter, what should I measure? And how much should it read?

Thanks

 

[Hunner]

With the button pushed you should have 12V at the diff end of the wire. If not start checking the source, ie fuse or other cut wires.

Dealer once destroyed my Eaton without checking for voltage while under warranty and claimed it was bad because the electro magnet was black and lumpy, but Eaton confirmed that was the way it was supposed to look.
Then it took them weeks to fix it after installing a new one that did not work.

I politely suggested they check to see if it had voltage at the diff end, duh!

 

[4speedfunk]

Just make sure you are in 4LO-lock when you check it. The locking diffs are defeated in either 4HI mode.

 

[OmarOHelmy]

It Worked

The connection I did the first time was bad, so i cleaned it up, and it just worked The diff locks and the button on the dash no longer flashes. And the error message disappeared...

Off course I have no to know if the diff is actually locking till next trip to the dunes, but for now I'm very happy.

Thank you Hunner and everyone.


Next weekend I want to take it to a garage to change the diff oil, transmission and transfer case oils. I bought everything from the dealer (including transfer filter/gasket kit)

I just need to buy a new gasket for the rear diff as well, because I want to open it and check the gears, drain the old oil and then close and fill.

My car has 108K miles, so it's about time I serviced these.

Regards,
Omar


PS. I did measure the voltage before reconnecting the wires, it measured between 2.5 - 4v it was not a very accurate measurement, because I was under the car and trying to hold the volt meter, connect the cables and trying not to burn my face on the exhaust

 

[OmarOHelmy]

Here are some pictures for the fix:

 

[OmarOHelmy]

On a different note, does anyone know what is the hose connected to the rear diff? Is it for filling the oil? it has a plug at the end

 

[H3slate]

On a different note, does anyone know what is the hose connected to the rear diff? Is it for filling the oil? it has a plug at the end

That is a breather hose for the diff. Shouldn't see any fluid in our it if that tube.

 

[OmarOHelmy]

Ah, ok

I thought it was for filling the diff oil