my rear diff lock seems to have stopped working ( no light )
had a look at the actuator all seems fine
there is a sound of leaking air from the three ball thingy under the floor
but front diff lock is working fine
took a pipe off the actutor and there was the sound of escaping air
does the light fail on the dash ever?
and can I test this by jacking up the car on the drive and rotating a wheel
t so see if the diff is engaged and its just the light not working
MAT
rear diff lock not working
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Yes Matt, you can test it this way, the spare vacuum from running the engine for a minute or two is quite enough to not need to have it ticking over as well... axle-stands are in order though!
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Syncro Kastenwagen / 16" Kombi Camper
Syncronaut No. 1
Because you want to be able to turn the wheels at will to get the lock to engage and then also skoot underneath when it doesn't and eyeball the bracket and vac actuator area with the vac in both positions, as well as quite often fiddle with the non-return valve and connections. Quite often the vac throttle unit will be cracked and leakiing on one side or the bracket distorted - eyeballing the whole thing closely is often the best way of finding where a problem lies. Matt should know whether his lock is on/off regardless of the light - a quick trip around a mini-roundabout soon clarifies that - so I'm presuming there's a problem somewhere down there. e were driving over loose rubble and rocks for a good few hours on the Saturday and Sunday so its posible something took a whack underneath.
The 80-90 Tech Wikipedia Your 1st port of call

Syncro Kastenwagen / 16" Kombi Camper
Syncronaut No. 1