Belt tensioner 1996 Corsica V6

I have just replaced the battery on alternator on this vehicle, and I am getting mixed results when having the battery and alt tested at the auto parts store. The car is charging fine, but when I shut it off it acts like it has a dead battery some times. I thought there may be a parasitic drain, but I'm not seeing anything when I hook the multimeter up between the battery and cable. When I look at the pulleys while the car is running the belt tensioner has a severe ratcheting action and I would like to know if this is normal or if the tensioner should be pretty much stationary?? How much of a PITA is it to replace it? could this be the reason I'm getting a bad charge?

I have just replaced the battery on alternator on this vehicle, and I am getting mixed results when having the battery and alt tested at the auto parts store. The car is charging fine, but when I shut it off it acts like it has a dead battery some times. I thought there may be a parasitic drain, but I'm not seeing anything when I hook the multimeter up between the battery and cable. When I look at the pulleys while the car is running the belt tensioner has a severe ratcheting action and I would like to know if this is normal or if the tensioner should be pretty much stationary?? How much of a PITA is it to replace it? could this be the reason I'm getting a bad charge?
Look at a similar vehicle with no problem it sounds like it maybe bad. It takes normally under 1 hours time if you know what your doing. Their is a pin in the back which has to go into the hole. Look closely or you will miss and find a grove in the block. Spin idler and other pulleys and listen for abnormal noise.
Make sure battery terminals are clean and tight.