I have just replaced both rear shocks and the Air Compressor on my 2004 Escalade - in the last 2 weeks. My air compressor comes on at start-up and runs for approx. 10 seconds. It then cycles on every few minutes for about 10 seconds. Is this normal? How often should the compressor cycle in a normal operating environment? No load or trailer. I can only hear it running when the truck is idling and I am outside of it. I bought the truck a month ago and the rear air shocks and compressor were shot, so I don't have any experience with a properly working system.