[takomaned]

Most voltage regulators have a thermister built in to reduce charge as the temp increases. I would expect a min.of 13.2 volts. Do you have a V belt drive or serpentine belt? Test the battery with a volt meter 1st.with the engine off. If you've been running the engine,turn the headlights on for 10 sec.to remove any surface charge. You'll want to see 12.6V. min for a good battery(new is 12.9V). Next look for a voltage drop on both positive and neg.sides of the battery. Engine running,(volt meter on DC volts) take the red lead and touch the output side of the alternatos,place the black lead on the POSITIVE post of the battery. You should see less than .3 volts (perfect is 0.0v) Also check the neg.cable the same way.Touch the lead to the case of the alternator and the other to the post of the batterry (neg).If you have voltage drop,feel the battery terminals. If they're more than warm,thats where the problem is. Also,make sure that the cars volt meter matches the hand held one.