I have a 2003 dodge 2500 diesel auto. My question is what is the electric vacuum pump for that is mounted on the passenger side behind the battery. Mine cycles on and off constantly and is very loud. any comments will help.

 

It is for the cruise control. I wouldn't think it would be cycling unless the CC was on.

 

Don't mean rob your thread, but small question

My cruise control surges quite a bit when i set it under 75. Could that be a bad vacuum pump or something else?