99 sierra instrument cluster

start last week dash went flat only signal/flasher works. then comes back on. next it starts to constant flickering thsn gauges go flat again.hit a big bump gauges come back up. worked for a couple days then the gauges go flat right out of the blue?? got another dash when i first put it in it worked for about a mile?? then went flat again ?? put old dash back in and still nothing but signals
checked connections all seem to be fine. i hear clicking behind dash once in awhile is it the body control module? any ideas?
thanks