On my 91 Accord EX 4 door sedan, the alternator intermittently stops charging for very brief periods. When it happens, the tach and speedo go to zero, and various other electrical items go on and off. Periods last from a couple of seconds to about a minute. The alternator was replaced, but it is still happening. It will never do this for the reapir shop, just for me on my way to work. Any ideas would be appreciated. Thanks in advance.