97 suburban lights problem

first all thanks for even looking. my problem is the lights on my truck like pulsate or something. when the truck is on idle the lights (DASH &HEAD LIGHTS) look like they are about to go out,but they dont and when i hit the gas everything is normal the truck starts starts with no problems,it has a new battery with 900cca and with the doors open no int lights but they work manualy. any body with some directon to where to start graetly appreciated . thanks in advance:banghead:

Search the forum. There are similar problems posted here. From what I recall, your symptoms indicate a alternator issue.