last night I parked my truck all was fine went to start it up tonight battery was dead. I put a charger on it and heard a clicking noise sort of like a vacuum pump running on the driverside under the air intake. the sound was coming from a module that looked like it said "kelsy-hayes " any ideas what this is. this happened as long as the battery cable was connected the ignition key was turned off, could this be antilockbrake modulel or fuel pump?.

 

I finally got a chance to take truck to a local dealer found out it was the antilock brake system He tried to charge $1300+ for repairs.the parts and labor wasactually coverd under warranty. Bad thing is he had to order parts and still has truck.

 

when my Explorersa battery drained & i turned the key I heard that but that was on the start, after my6 battery was jumped never heard it. Was your truck running hearing that?