Until my 318is reaches operating temp. here in wintry NYC speedo & tach do not work at all. As it reaches operating temp. speedo resumes perfect function, then after 20 minutes or half an hour tach very gradually starts registering, at first only when I rev it hard - and at this point it is reading inaccurately and erratically, then, finally, after 45 minutes or so tach resumes nearly normal operation - though I suspect it shows idle speed as at least 500 rpm lower than it really is. Anyone ever seen these problems or have a good ideas how to remedy? Thanks and cheers, TOM