Mark. Is this on a 74-78 Auto Temp? If it is, your problem is that the check valve in the vacuum resevoir is toast. These are dead simple to replace and easy to come by. You just replace the soup can under the hood. ----- Original Message ----- From: "Mark Blitman" <fedsales@xxxxxxxxx> To: <mailing-list@xxxxxxxxxxxxxxxx> Sent: Thursday, November 06, 2003 10:50 AM Subject: Re: IML: Auto Temp II buzzing...... zack..i get a similar sound but i have always attributed it to the fan when it runs at middle or slow speed and makes a noise..does your a/c cut out on acceleration? mine does and i have not been able to locate the cause...