My car stalls at idle and the lights get dim , when I am moving no problem on 2003 Chrysler PT Cruiser

when I am at a stop the car wants to stall and does stall from time to time. the interior light dim off and on have a battery thats only 3 months old

Asked by for the 2003 Chrysler PT Cruiser
Check the battery for full charge, and CCA are a least half of the amount listed on the battery. If it is low charge the battery to full. Next check the cables for loose or dirty connections repair as needed. Next check the belt to altenator, and belt tensioner the belt should be in good condition and tight. Next check to be sure Alternator is putting out about 14.5 volts if not and everything else has been checked and ok the Alternator may be your culpret, it may just be charging enough to keep engine running with no electrical components running. Many new batteries come off the shelf needing a charge, who knows how long they been sitting on the shelf waiting for you to come buy them.
1 more answer
check egr valve if you've been usuing different low grade fuels