Rear diff lock woes again!

[Spike]

Morning all, new rear actuator fitted about two and a half years ago, working fine, used it probably only once last year, though I had better give it a spin,

 

[Spike]

sorry hit wrong button, i could hear the relay click in the cab and a fairly loud whirring on the actuator but no way could I get it to lock, tried gravel and circles no joy, so took it out and stripped the motor down, the actuator rod had correded to the alli casing and stuck fast, took some shifting but with a good clean and some lube got it moving easy, connected to 12v supply and it worked, put it back in, in the locked position, turned on the ignition with the locker switched off and the actuator unlocked, excellent! tried the lock from the switch and nothing no relay click and no whirring at the actuator, so I seem to have freed the locker but f***** something else up, does anyone know where the fuse/relay is so I can see if its something simple, I know alli and steel are not a good mix but quite suprised by the amount corrosion in the case after such a short time. Many thanks