I installed Nordskog Digital guages in my 91 Mustang a few days ago. They work well except now whenever I turn the car on, the car will beep 5 times in a row, wait about 3 seconds and then do it again. It does this about 5 times and then stops. Then after exactly 30 minutes of driving, it happens again! The exact same 5 beeps 5 times and then it goes away. It does this exactly every 30 min. What is the cause of this beeping?