The dreaded GU factory locker fault finding

[thatowensbloke]

Hey all,

sorry to create a new post, didnt seem right piggy back on the end of the others as they were a bit old.

I have a 2012 Y61 ST ZD30 Manual, with the factory rear locker.

Over the last few weeks, i have been getting a flickering of the DIFF LOCK LED on the dash, but it generally goes away.
It has lit up solid only once before (other than when i am actually using the DL), but now i have 4 LEDs lit up and the locker is actually engaged.
Doesn't matter what the transfer case is in, or where the locker switch is, the DL is engaged. You can hear it when turning (i am not driving it, this was troubleshooting).
Today i was in 2H and Diff Lock OFF - yet it was still engaged. i parked the car again, and started to troubleshoot.

So, i have searched the posts, and it seems that generally the solenoid is the problem. My symptoms seem a little different, so i wanted to see if anyone had some ideas.
If i remove both vacuum lines that run to the diff, i get vacuum constantly from a single port on the solenoid - regardless of switch position. no vacuum is on the other port, ever.
Testing the wires in the plug seem to indicate that the switch is working, as the voltage is seen on one wire when switched one way, and then seen on the other wire when switched the other way.

If i remove both vacuum lines at the same time, could this cause the strange behavior? i can see from looking at the unit that there are 2 unique solenoids within the assembly that are switched via the wiring loom.
apart from the input line, there is nothing in common with them that i can see.

Could i have 2 stuck solenoids - 1 stuck open and 1 stuck closed? can i blast them with an air compressor to try and unstick them?

Ive been looking into the MAC solenoids, but i really just need to get back on the road as its my only form of transport. any ideas?

Cheers
Tim

[Truckus]

Some handy reading here https://www.patrol4x4.com/threads/factory-vacuum-diff-lock.37095/

3rd post starts to get on the money for decent fault finding and a few after that as well

Also feel free to drop by and say G'day in the introductions topic for new members.

[thatowensbloke]

Cheers Truckus! I hadnt actually come across that one, the wiring diagrams will come in handy.

And yeah, i have been a background member for years - generally i have been able to find what i am looking for without posting ;)

[stevemc181]

Try swapping the vaccum lines with each other at the diff. If it disengages, then you'll know you have a solenoid problem.

[thatowensbloke]

ok, i found the issue - both the cause and the problem.

The cause was the vacuum line for the disengage side had fallen off near the rear trailing arm pivot. This must have sucked a pile of dirt into the solenoid, seizing it up.
The way i found this was to spray some windex into the hose at the solenoid end, and push some low pressure air down the line with my compressor.
Under the car i could then easily spot the foam and spray, identifying the problem spot real quick.

As noted earlier, I had already found that the solenoid was still producing vacuum on one of the ports, so i switched lines at both the solenoid end and the diff end, and successfully disengaged the locker.
The solenoid is still rooted, but at least i can get mobile again in the short term until a proper fix is completed.

I'll order one of the MAC kits from Patrolapart, and get it all sorted out once and for all.

Figured i should come back and post what it was for any future troubleshooters! My symptoms were an engaged locker in 2H with the diff lock switch disabled.
I had 4 LEDs lit up solid on the dash (Diff Lock, ABS, and the 2 Stability lights).

Cheers all!
Tim.