OT Mechanics: Battery/Alternator Question

quote:

---

could a faulty alternator be caught by just hooking the computer up and pulling codes?

---

Not a mechanic and don't claim to be one but I'm pretty sure this is possible.

I thought so as well, but my idiot light isn't on. Figured if I was having an issue with a faulty alternator, my check engine light would be on.

yeah you oughta have some sort of alt. light illuminating on the dash. but if the battery is really dead (can't charge), there's no code for that or dash light.

quote:

---

Car wouldn't start (no cranking at all) last night, so this morning before work, I jumped my battery off. Car started fine, but as I was driving, when I would slow down, the lights would dim, and eventually, at a stop sign, my car died again. I figured that my alternator would charge my battery at least a little. Could it be just a bad battery? Also, could a faulty alternator be caught by just hooking the computer up and pulling codes?

TIA

---

You need an alternator.

quote:

---

I thought so as well, but my idiot light isn't on. Figured if I was having an issue with a faulty alternator, my check engine light would be on.

---

I'm far m ore familiar with Caterpillar equipment than automobiles, but I believe the only indicator light you'll get is one telling you you've got low voltage. It won't tell you if this is due to the battery or the alternator. The best sure fire way to tell if the alternator is the issue is to take the car to Auto Zone and let them test it to see if it's charging.



Having said that, I'm about 99.9% sure you've got a bad alternator due to the fact that you jumped it off and it later died while you drove it. If an alternator is working properly, this should never happen.

Just to clear some things up in this thread... auto parts stores can not properly check an alternator in the car with a bad or low battery. Their tests go through the battery and can give false readings... most now have equipment that will say "bad battery, replace battery and then retest for alternator". When alternators go they usually take out the battery too. That means you will probably need new battery AND alternator. Be careful not to kill a new battery with a bad alternator

Alternators can be bench tested out of the car which is something you should do before replacing.

Had same issue last year. Had to jump off to start. Parts store (auto zone) tested and it was a dead battery. No problem since new battery was put in.