door locks don't work below 20 degrees F
 

200 4-matic wagon.... door locks don't go up or down but exterior lock actuator indicator lights work, so does alarm system if open door after pressing lock button on key. Dealer says vacuum motor must be bad. Says it costs $720.00! 1 - do you think vacuum motor is bad? 2 - if yes, where can I buy it, what is part #? thanks