Thanks, it's due for a scheduled service in about a month so I'll bring up the pump issue with the Service Rep then but I was just trying to get a rough idea of how often it should cycle for my own knowlwdge. It just seems to be going on and off more often than it did before.If so, is this a sign that the pump is going bad and should be replaced? I always like to have an idea what is going on before I go to the dealer and so far, I have had some excellent input from this forum both on my E320 wagon and on my 85 280SL Euro......Desert