chirp

Started with chirping under hood near center of dash on a trip last Monday, only when AC is on and only when accelerating from a stop to about 30mph. Then, day 2, add a vibrating noise to the chirping, which sounds like something is about to break, and stops if I let off acceleration or turn...

I bought a used 2006 Tahoe. When I first got it the alarm would chirp when turned off or turned on. Now when I hit the button on the key fob, the alarm does not chirp but it does enable the alarm. I know the horn works because if I double lock the car or hit the panic button, the alarm sounds...