The older factory alt did not put out full charge at idle. Even the output test in the service manual says run the eng at 1500 to 2000 rpm. But the newer Power Master should charge good at idle. We put this one wire 100 amp Power Master alt on my sons Dart and it puts out much more at idle as it put out 70 amps at idle when I put a load on it. We like it because it looks like a stock Mopar alt. You don't have a larger alt pulley on the car do you ? Many racers put the larger alt pulley on for more hp but it kills the charging at idle. Ron