How to Unfreeze a Frozen Car Lock: When the thermometer dips below freezing temperatures we receive calls from customers who are locked out of their cars because the car door lock is frozen. Note: the most common cause of frozen car locks is the customer washed their car and not only is the car lock frozen but the entire door. Most of the time only a small amount of water has entered the car lock via the keyhole. Do not pour hot water over your car door and car lock. I have found the best method to loosen up the frozen lock is using a spray “Lock De-icer” and it is available at most Automotive Stores.