Dilute liquid detergent with water in a squirt bottle. Have an assistant inside the cab with an air hose. Begin the test at the bottom of the window and gradually move up the window edges and across the top of the window. Squirt soap solution on the window moldings and the glass on the outside of the vehicle. Have an assistant aim the compressed air at the same locations from the inside of the vehicle. Do not exceed an air pressure of 205 kPa (30 psi) from the hose. Bubbles will form in the soap solution at the location of the leak.