Air systen cycles (blows off pressure) every three seconds

bob b wrote:
New update. It was the check valve! This is a small one inch rubber face metal disc that works with a spring to maintain pressure. It is located in the dryer just under the fitting for the large hose connection. I removed it and found damage to the rubber seal. Good news,! It is easy to change, cheap, and rewarding to fix. Thanks to the help on this topic. Bob