Need thoughts, low occ. voltage

[Ramblin Fever]

Have no idea where to turn, with the exception of replacing Battery cables - only thing I haven't done yet.

Here's the issue; bout 5 months back, all belts replaced. About 3-4 months back, both battery and alternator crashed on the same night. Alternator croked while doing 65mph coming down I-70, battery and brake lights came on, voltage dropped to 11 or so.

Pulled off highway, drove 2-4 miles up road to a Wal-Mart, only place open. Per their car shop, battery was corroding and starting to swell; I knew both the battery and alternator were getting up there. So this was no surprize, they threw in a new battery, cleaned up the end cables, etc etc.

Obviously they couldn't assist with the alternator (wouldn't have let them anyway), truck fires right up, both idiot lights still on, at this point I still had another 60-some miles before actually reaching Denver. The bearings in the alternator were still allowing the belts to turn, (have 3 driving belts) and everything seemed in check, aside from 11-12 1/2 voltage.

Truck got us into Denver just fine, parked her for the night, but left the battery on the charger, seeing as it was almost dead - having been the only thing giving voltage. Next morning a remanufactored Isuzu alternator is installed, even dealership no longer carries brand-new ones.

Voltage comes nicely back up to 14-15, truck runs great. However, ever since then, the stupid idiot lights are still very slightly lit. Readjusted the belt and put on new battery clamps, still have lightly lit battery and brake lights. And, on occasional take off's from a light, those 2 lights come on real bright, volts drop to 11.

I've read that it's normal for Izusu's to do this, per owners manual. But, not like this, at least I don't think so, as I do not stomp on the gas pedal, and it seems more frequent when it's hotter out.

I have A/C, but haven't been using it. Truck's running fine, no other idiot lights, tranny's shifting normally, however, at times there's a bit of sluggishness, and always shows when volts are at 12. So I know it's because it's losing voltage somewhere.

Anyone have any ideas - battery, alternator, and belt check out fine. Dad was thinking corroded battery cables?? I have kept this baby in very good mechanical shape, but must admit, I've never changed out the cables. Is this something that needs done after 100K miles or so?

Thanks!

[95.5 Rodeo]

I think I've read other threads about weird alternator / battery problems like this but I don't remember what the solution has been. Maybe someone else knows. It's a good idea to check the battery cables but maybe the "new" alternator has an intermittent problem.

Good luck,
Dale

[tomlcollins]

sounds like you have a bad connection/corrosion somewhere. I would replace battery cables and make sure all of your connections (INCLUDING STARTER) are clean and tight. If this doesn't fix it, then I would suggest that it's the following: your warning light is most likely controlled by a source outside of your alternator (some type of resistor, ohmmeter, etc.). whatever activates the light has gone bad and needs to be replaced. either buy a service manual (ACTUALLY THE FIRST THING I WOULD DO REGARDLESS OF THE PROBLEM) and trace the wiring to find out what it is, or call the dealer and ask someone in the service department (although they will probably try to get you to bring it in). I wish I could give you a more definite answer on what controls your light, but i've never experienced this problem firsthand with an isuzu before.
changing cables is not something you normally do as preventive maintenance. it's something you end up having to do in situations like yours. good luck, let me know how it runs with the new cables.

[2eyefishclaw]

if you are getting 15 volts from the alternator that is most likely going to be the problem its too much

[tomlcollins]

As long as you're not going above 14.6 or so, you shouldn't have an overcharging problem. I'm guessing you have a voltmeter installed inside your Rodeo (I have an 02, and am not real familiar with the instrument panels of a 97). You mentioned some sluggishness when the volts are at 12, are you measuring 12 at idle?? That's too low if you are. Slice your positive battery cable open (after disconnecting the battery of course) and see what's going on in there. If there's no visible corrosion, then move on to your connections and tape the cables back up with electrical tape good and tight.....i'm going to check some specs i have at home tonight and get back to you tomorrow if you still need help

[Ramblin Fever]

Originally Posted by tomlcollins

As long as you're not going above 14.6 or so, you shouldn't have an overcharging problem. I'm guessing you have a voltmeter installed inside your Rodeo (I have an 02, and am not real familiar with the instrument panels of a 97). You mentioned some sluggishness when the volts are at 12, are you measuring 12 at idle?? That's too low if you are. Slice your positive battery cable open (after disconnecting the battery of course) and see what's going on in there. If there's no visible corrosion, then move on to your connections and tape the cables back up with electrical tape good and tight.....i'm going to check some specs i have at home tonight and get back to you tomorrow if you still need help

Yep, I have a voltmeter in the truck. At idle, she registers between 13-14, and at cruising speed it's right there as well. It seems to be upon even the lightest take-off from a light, corner, etc that the volts drop to 11-12 and the idiot lights come on bright.

I think I mentioned before that I have read that Isuzu's do this as an economic trait; however, I don't feel that it should be to this extreme.

The volts have never gotten to 15 or above; but I only faintly ever remember my volts dropping to 12 in the previous years of owning this truck, even on harsh take-off's, which I've rarely done.

Thank you greatly for your help.

[Ramblin Fever]

Originally Posted by 2eyefishclaw

if you are getting 15 volts from the alternator that is most likely going to be the problem its too much

It gets real close to 15 at cruising speed, but never actually 15. My problem is the truck, in town, stop and go traffic can't seem to hold 13-14 volts at all times. It frequently drops to 11-12.

Open highway, or steady speeds, she's at 13-14 without a prob.