Can anyone tell me how this thing works? I had to disconnect it in order to remove the gearbox. I am fairly confident that I reconnected everything the way it was.



When I pull the switch, nothing happens. If I swap the clear and red tubings, I can get the diff lock to engage but then it won't disengage until I swap the tubings again.

With it hooked up as the picture above, I can hear vacuum noises come from the switch when the switch is pushed in but not sure if this is normal.

I've looked at picking up a new one, but these things are expensive! A few hundred quid!

on the side of the of the front output housing on the transfer box is a diaphragm actuator depending on which side has a vacuum depends on whether it puts it in or out of diff lock, the switch has a vacuum supply from the engine ,and 2 pipes 1 to each side of the actuator, if it works one way but not the other either the switch is piped up wrong or switch leaks on one side so unable to hold the vacuum

jamesmartin said:

on the side of the of the front output housing on the transfer box is a diaphragm actuator depending on which side has a vacuum depends on whether it puts it in or out of diff lock, the switch has a vacuum supply from the engine ,and 2 pipes 1 to each side of the actuator, if it works one way but not the other either the switch is piped up wrong or switch leaks on one side so unable to hold the vacuum

Click to expand...

Should there be vacuum present from both sides of the switch to operate the diaphragm or is it a vacuum on one side and a vent on the other? I'm just trying to make sense of the vacuum noises I am hearing from the switch. Seems like everything points to a leaking switch I am just trying to avoid spending that much. I didn't touch the switch as part of this job other than to disconnect the vacuum hoses. Seems odd that it would have gone out at this moment.

vacuum is switched from one side to the other, so you should have a vacuum on whichever side dependant on switch position and vent on the other, if it operates one way the actuator diaphragm is ok but is only getting a vac to one side, though whilst testing it helps to have 1 front wheel jacked up so you can spin the wheel to ensure the splines for diff lock align and to prove its going in and out , wheel wont spin when diff locks engaged but will when not

I am now fairly convinced that it is the switch that has gone bad. I've done several tests and the switch works in one position and not the other.

Next step will be to attempt to disassemble the switch and see what we have. What's there to lose since the switch is bad anyway?

As these things are quite expensive for what they are, I may just end up putting in a 3-way solenoid with a switch on the dash as a replacement.