The 80 got parked for a couple months at Panama Passage and now the diff locks won't engage. the lights are flashing (front and rear) but that's it. they were working before we parked it. As far as I remember, the truck does not have to be in low-gear or even 4x4 to activate them, right?
I haven't had much time to do any research online yet, sorry about that - but what would be the first thing to check?