lawsoncl

You have a poor understanding of how alternators work and how they're controlled by the pcm. Alternators put out an a/c voltage that gets rectified by the diodes. It's not a steady voltage without the battery attached. Also if the battery is fully or nearly fully charged when you yank the cable, there is no guarantee that the pcm is going to react fast enough to increase the field coil voltage in the alternator to maintain any output current at all.

Dave51

Is that because PCM sees volts or because of a completed circuit? If he wired a 12 volt something (like a headlight) in parallel such that it would maintain continuity when the cable is yanked, would that maintain stability? I'm kinda thinking it would, as previously noted an absolutely dead battery doesn't blow alternators.

I need to find an absolutely dead battery and measure it's resistance...

Dave51

I would also offer that the alternator is not properly grounded, but since the OP says it's new that probably isn't it.

But I have another question. Why are we doing this in the first place? Isn't this an "If it ain't broke" thing?

gat

With the engine running it not does touching the disconnected negative terminal and the ground at the alternator show ohms or beep for a multimeter continuity test? Same thing for positive side of things?

lawsoncl

Exactly. He' already done a better test by measuring the voltage at the battery, which said he's getting charging. Yanking the battery cable is a pointless test that puts the electronics at risk, and doesn't provide any conclusive answer. If you really want to test the alternator output, do an actual load test. Most autostores will do it for free.

Jeremiah Joyner

Did you ever figure the problem out I'm having the same problem. Theres too many idiots commenting to scroll through and read everyone

lawsoncl

That's a sure fire way to get help. :/

Start a new thread and describe your problem, including year, what troubleshooting or parts replacement you've done. Also whether it's a new problem or a pre-existing problem on a vehicle you just bought.