electrical issues gmc sierra ’95’

i have a 1995 sierra 2500 series 5.7 gas engine. my horn and my washer fluid arent working. i cleaned all my ground posts. put in new fuses. wen i hit the horn you can hear the relay switch clicking. and when i first went to use the washer fluid it squirted once then stopped. i took out the horn and the pump hooked them up to a battery and they both work. i cleaned all my ground posts with no go. any clues???