I have a 2002 c240 which is starting to make a clapping sound everytime I start it. Its seems to be originating from behind the main blower vents on the dash. I believe it may be associated with the climate control but not sure. The noise stops after about a minute, but the air flow does not seem as strong as it used to be. My care has about 1000 left on the warranty. Any ideas what this might be or how serious of a problem. Thanks in advance! moman