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2003 Eclipse Alternator Problem

well, that was easy…

Good for you OP.

For those interested, I measured the voltage drop on my Corolla again this AM, between the alternator B+ post and the battery + post.

Ambient: 80 degrees F
Car not driven for 14 hours prior.

After starting and idling 2 minutes:
99 mv

Same as above, but headlights on bright and heater fan on max
275 mv

Thanks everyone.

Interesting . . . when I bought the new alternator, and set the old one on the counter, a second guy standing there said, “Didn’t I test that about a week ago?”

Well, yeah.

:innocent:

1 Like

@ok4450 writes …

“purpose or logic behind testing the battery to alternator lead with both probes of the VOM and expecting to get a voltage reading”

Another way to think about it, that’s similar to how a dash alternator current meter works. The voltage measured is directly proportional to the alternator’s charging current. See the post above where I re-measured it on my Corolla, in two different current-load conditions.

This happened to me took my alternator to oreilleys 3 times and it tested good so i tried every possible path i could think of that caused alternator to not charge.(even ran wires direct from battery to alt.in case harness had break).**Then i read online about doing diode test on alternator and youtubed how to do properly and finally i found itWAS the alternator failed diode test.so i took it to oreilleys and told them i wanted it replaced cuz the diode failed (i even took my multimeter just in case i had to show them how i found it to be faulty😁)but the chick realized it was easier to do warranty swap than test again and them say it was good alternator because i would have argued til they found me to be correct anyway, then i got new alternator and changed right there in parking lot in 20 min.(alternator was still hot from driving there)but i was ready to get my car back normal again and excited that i figured it out.(this was all on 03 Galant but its the exact same engine setup so that why i put on here.) Sorry post so long and know this is old post but im posting for others like me surfing forums looking for answers.cuz it only takes one persons tip to get goin in right direction leading to getting your problem fixed…and thank you to all yall who posted on here as this thread hepled me figure out current issue im having with bad ground.much appreciated👍

Wow! . . . . from my poor memory, unless it was something 50 years ago . . .

I recall my O’Reilly’s failing again, and this time the mechanic I took the car to called them, and they brought him another one, no problemo. That’s been a couple of years ago, and it’s doing fine.

:mask: