2002 lincoln ls check charging system

2002 ls with 111k miles. 2 months ago replaced battery and alternator because of alternator failure. last couple of weeks when i start it up in the morning cold and after starting the and the rpms are back to idle "check charging system" comes on. dash lights seem dim and heater doesnt blow as much as it should. after about 10 mins of driving the lights appear brighter and heat blows correctly and check charging system light goes off. its almost if theres not enough power then it surges after 10 mins and runs correctly. Is this a electrical or another failing alternator. it seems it only does this on the first start of the day. i would like to fix this problem before i try and sell. Dont know if it was a refurb or new alternator.

Aftermarket alternators don't seem to last very long at all on the LS. I don't think that you can get new Motorcraft any more either. You'll have to get a refurbished Motorcraft from a dealer.