problem? alternator help.

lillitnn92 · 04-06-2005, 05:05 PM

never tested an alternator, how you do it?

my battery light came on a half hour ago. i just replaced the battery and alternator at the same time a few weeks ago. i multi-metered the battery and i'm getting 12.65VDC, so the battery should be fine. i tested on the posts and in the cable to make sure it wasn't loosing it from the post to the cable. and the truck starts still, so it's putting out the amps.

i previously had an alt problem and could tell it was bad from volt gauge. at idle it would drop and at higher RPMs it came back up. this time it's dropped down to about 8V and staying there along with the battery light being on. i'm gonna try an reset the computer first and see if that does anything.

Andy · 04-06-2005, 05:14 PM

Get voltage with car running, ~13.7-14.9 is safe. Too low and it's not charging yourbattery, too high, and it's cooking stuff. Just go to Autozone/Advance.

BLINGMW · 04-06-2005, 05:20 PM

lillitnn92 Wrote:at idle it would drop and at higher RPMs it came back up.

you replaced the alternator, is there any chance you have an external voltage regulator? I think MOST if not all are integrated into the alternator, but if that failed, you might have those symptoms.

lillitnn92 · 04-06-2005, 05:48 PM

BLINGMW Wrote:
lillitnn92 Wrote:at idle it would drop and at higher RPMs it came back up.

you replaced the alternator, is there any chance you have an external voltage regulator? I think MOST if not all are integrated into the alternator, but if that failed, you might have those symptoms.

well, that was before i replaced it a few weeks ago. since then it was holding like it was supposed to. now it's just dropped and staying, not moving at all which made me think it was the battery. it is externally regulated. i'm going to take it to advance tomorrow and get them to test it if they can.

lillitnn92 · 04-07-2005, 06:54 PM

this afternoon.

okay, i went to advance auto. ran the tester on it and battery is fine. with it running however, it was only putting out 12.20V and it should be much higher than that. the tester also said there was no "output" from the alt. which he said could be either alt or bad wires. so, we take mine off, and test it. wouldn't even test or he was having trouble, so he gave me a new one. i hooked it up and got in a convo with a guy who had a bronco II that was nice and all and forgot about checking to make sure it was fine before i left. so i get about 1/4 away and remember. i still have the same problem.

30 minutes ago.

don't think it's the wires. i pulled the wires completely off and did continuity tests and everything was fine. i took the fan and subwoofer positives off and it was still there. the only thing i haven't tried is unplugging the MSD box, but that's something i'll try tomorrow. i either got another bad alt, or i have something that is making them go bad. i'll leave it over night with neg off and see it it goes away.

***ViPER1313*** · 04-07-2005, 06:57 PM

Regulator. Have you tried shunting the alternator to force it to charge?

lillitnn92 · 04-07-2005, 07:03 PM

ViPER1313 Wrote:Regulator. Have you tried shunting the alternator to force it to charge?

explain please :oops:

***ViPER1313*** · 04-07-2005, 07:32 PM

Sorry, I meant full field the alternator :roll: . Instead of having the external regulator tell the alternator to turn on and off, just hook the wire going to the regulator to the + battery terminal (momentarily.) You should hear the engine slow down a bit since the alt is charging full tilt. Hook up a millimeter to the battery while you do this and watch the voltage.

**Mike** · 04-07-2005, 10:25 PM

ViPER1313 Wrote:Hook up a millimeter to the battery

hehe gotcha!

lillitnn92 · 04-07-2005, 10:29 PM

Mike Wrote:
ViPER1313 Wrote:Hook up a millimeter to the battery

hehe gotcha!

dammit, and i was looking hard for my millimeter, i know it was in my toolbox last time i used it.

***ViPER1313*** · 04-08-2005, 02:35 AM

fuck english

christo · 04-08-2005, 02:48 AM

I thought we weren't fucking allowed to cuss in the technical forum

Andy · 04-08-2005, 08:43 AM

ViPER1313 Wrote:Sorry, I meant full field the alternator :roll: . Instead of having the external regulator tell the alternator to turn on and off, just hook the wire going to the regulator to the + battery terminal (momentarily.) You should hear the engine slow down a bit since the alt is charging full tilt. Hook up a millimeter to the battery while you do this and watch the voltage.

I've never heard of that. Interesting. Is there a chance of electricution?

***ViPER1313*** · 04-08-2005, 09:43 AM

christo Wrote:I thought we weren't fucking allowed to cuss in the technical forum

Fuck that :roll:

jackstands Wrote:I've never heard of that. Interesting. Is there a chance of electricution?

No. There is a chance that you will boil your battery acid though if you keep it hooked up like that. Just don't do it for more than a few seconds at a time.

lillitnn92 · 04-08-2005, 01:13 PM

SON OF A B#%@$*!!!!

i went through all that for the past couple days and it was a DAMN 15amp FUSE!!!!!

i was only looking for fuses i thought were related to the charging system. before, so i never saw this one. well today, after buying a new serpentine belt thinking maybe mine was a little stretched, it didn't work. so i pop the fuse panel again and was looking and saw a 15amp blow. it says something like "engine comp ??" don't know what that is supposed to mean, but dammit if it wasn't the f'n problem.

ScottyB · 04-08-2005, 02:59 PM

hahaha, i hate to laugh at your misfortune man, but that's funny as hell.

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