How do I fix the clock on my car?
Why does my clock keep going off?
The most common cause of an analog clock losing time is that there is buildup in the battery compartment that is keeping the battery from connecting fully with the clock mechanism. Remove the battery and check the leads to see if there is any buildup from a leaky battery, dust, etc.
Why does my car clock keep slowing down?
Simply because it has in independent time base. Even if accurate to 10 parts per million, that is . 001%, it will drift about a minute per month.