strange problem

Ok first excuse the length, but you need to know all to possibly help me. I got my escape in February and it started running rough I ended up replacing the battery, tesioners, belts, alternator and major tune up. now 5-6 months later my escape started running rough again, I troubleshooted and every thing led to the alternator. I pulled out and had it tested and it was dead. I got a new one under warranty and installed, and all worked good again until. the first time i went through this i bought a voltage monitor that plugs into the cigarette lighter and have been monitoring it while driving the past few days since the alternator was replaced. I have noticed that when I first start up it is all fine, but when i am fully warmed up and go from any speed to a stop the voltage will go from normal charging of 13.5 - 14.2 volts down to 12.25 volts and as i sit idling it will slowly discharge the battery. I thought it was the ac because it has been 105 around where i live, but i drove for a while no ac and pulled the fuse just to be sure and was still happening. I have never seen this much drop between driving and idle.. any ideas ?

thanks in advance guy and gals

Dale :rockon: