charging issue ??

[lt704]

Hi Folks, My 2003 Chevy Silverado starting giving me problems the other night. It was a bad alternator. The truck kept dying. I put in a new alt. because the old one was not charging. The truck runs fine ( not dying ). The problem I am having as I drive the the heater blow almost dies when i hit the brakes but runs normal as i drive with increased speeds, the same is tru with my powere windows. I checked my battery, It is good and also good underload. My alt is reading 14+ volts when truck is running ( with battery/alt tester ) My truck has the 4.8 engine and a 105 amp. any ideas??? thank You Russ