Trying to fault find the rear factory locker in the 2013 GU.

At the diff end, with engine running and locker ON - No vacuum on the top hose
At the diff end, with engine running and locker OFF - There is vacuum on the lower hose

Tested vacuum at the solenoid.

With the locker ON, I have vacuum on the top outlet of the solenoid.
With the locker OFF, I have no vacuum on the lower outlet.

I measured the voltage going into the solenoid, there's a pink and a blue wire.

With diff ON - Pink = 0v
With diff off - Pink = 13.xV

With diff ON, Blue = 13.xV
With diff OFF, Blue = 5.6V

Most times the locker doesn't engage, but after all this checking I took it out and it did engage, not immediately, I had to drive for 10 metres or so before the locker engaged.

That 5.6V reading doesn't look right to me and knowing these things always die, I'm thinking I should just replace it & be done with it.

What do others think?

Thanks for any help.