o4 grandmarquis ls battery drain

Is there anything installed that doesn't go through the fuse box?

do you mean anything aftermarket? if so no. Everything is stock

Battery is new and holds charge but over time loses charge due to a draw somewhere

no air shocks, no light on or heat

The alternator is one suspect, disconnect the power wire from it (the heavy one) and re-check. This is my specialty. If you hook up a 12v light bulb between the batt. pos and the car does it light up? If not, use a seat belt buzzer or such. It will buzz and drive you crazy, but then disconnect wiring harnesses and devices until it stops. I bet it's the alternator, I ran a cross a ford doing this. Disconnect all wires to it when testing. Bad diodes, or regulator inside.

thanks will try and get back

I used a volt meter on battery ground and put the positive side on the wire harness part of alternator. I was reading 3.76 volts when car was in the off position. So, it must be the alternator trippmeister because their should be no draw from alternator when car is off. Thanks .

I'm having the same problem, replaced 2 alternators and 2 batteries had the same problem took it to the shoot they said my radio fuse was the draw so he took it out and still having the same

Hi CJ. This thread is 8 years old. Please start a new thread so everyone can see your question and be able to help. Jim