Without taking the mirror off (sometimes they will break coming off)you can check it out by moving the mirror all the way out and pry the inside corner out enough to see the connectors. With a pair of needle nose pliers you can disconnect the two connectors, use an ohm meter to measure the mirror if you have no resistance then the connectors were more than likely making bad contact, clean off the connectors with a jeweler's file and reconnect, this will often fix the problem. If the mirror heating elements are open then you will need a new mirror. THe part number for the left mirror is 9171314, don't know the price.