My Grand Marquis has a good battery.
It has air suspension and every once in a while I hear the pump running when the engine is off.
Other than the draw from the air suspension compressor, I know of nothing else that would tend to draw the battery down.
When the battery is discharged, usually after sitting for a few days, there is only a click sound from the starter.
After I jump start it and run a half hour errand, it is fine for another 90 days or so.
I have a DC clamp on meter, nothing noted.
How would you go about diagnosing this intermittant electrical problem?
Thanks,
BoyntonStu