Each time my central A/C turns on, there is a loud buzz for less than a second from the CB panel, then the A/C comes on and runs just fine. The A/C is a new unit, but I recall hearing the buzz with my old unit for many years and thought it was related to that. I have 200A service but the panel was installed in the 70's.
I had the cover off and when the A/C turns on I don't see or smell anything.
Any ideas or suggestions would be appreciated.

The buzzing is coming from inside the circuit breaker, and it most likely will fail someday. Either replace it yourself, or have a tech come on to replace it.

If you replace it yourself, you should shut off the main so the bus bar the breaker needs to plug onto is dead. ANy new circuit brekaer must be HACR rated, which will be stamped on the new breaker. Most brands are all rated, just make sure.

Thanks for the advice. It was an easy fix. I just needed the information and encouragement that I was doing the right thing.

What Brand Of Electrical Panel is It?

This is call wire whip. 2 things I need to know where is the 2 pole breaker located in the panel and the wires are bunched up in the emt and need to be twisted together. If your 2 pole breaker is not installed in the top part of the panel underneath the main. It pulls a lot o amperage on start up.