I posted about a possible short in my alternator in the electrical section... turns out it was a wiring issue. However, I do have another observation about the alternator...

When I first start the car, I read 14.5 volts across the battery terminal. However after everything warms up, the voltage drops to about 13.5. With everything on (stereo, electric fans, headlights, etc), that number will drop to about 13.2. Now, the even stranger thing is that the scanner will show that the ECM is seeing about .6-.7V less than what I read at the battery. But when I back probe the ECM connectors with a volt meter, I see only about a .1V drop from the battery. What gives? Is the alternator on the way out? Shouldn't I be getting over 14V at any condition?

It's a CS130, 105 amp alternator.

 

There will always be a slight difference in testing Equipment readings anyway.

There will always be a slight difference from the battery to under the Dash also.

I think most would agree that unless your falling in to the 12V area you don't have a problem at all.

Some of the older style Alts were 13.8V units. I would say that if that as longs as the battery is not to far from the engine bay (if it's not in there) and in good condition and the Battery leads are really good heavy gauge ones, and you have a good earth to both the engine and frame, along with all the cabling connections in the fuse panels clean then slight variations like this are 100% normal.