A small motor running

If this is for the Lincoln Town Car it is most likely the air suspension compressor. If the air suspension system is leaking, it will cycle the air compressor excessively causing a premature failure, and possibly a dead battery. I suggest having this vehicle diagnosed by a qualified mechanic to determine what needs to be corrected. You may need new rear air springs or other components, you could even do a steel spring conversion to eliminate the air suspension however this will light a suspension warning on the dash.