jmherman1993

So I have done some google searching and haven't found any other people that have had the same problem as me, so here I am. As my last question was answered so well I figured I would give it another shot.

The problem has to do with my battery light in the instrument cluster. I am going to try and explain this as best as I possibly can but it might sound weird so bear with me.

When I accelerate, no matter how much whether just a little bit or a lot, the battery light comes on and stays on for as long as I am accelerating. Then when I let off the the gas and coast, the light goes off and stays off as I am coasting and stays off until I come to a complete stop. As I am sitting at the stop with my foot on the brake and the car is in park, the light then comes back on. Something else to note is that this only happens when the A/C is off. But when the A/C is on at any level the battery light stays off the entire time no matter whether I am accelerating, coasting or sitting still.

I took my car to Advanced Auto Parts and had the battery, alternator, and starter tested. All tests came back good, meeting or exceeding industry specifications. Cranking results are good, voltage is good and everything else. I have a bluetooth ODB II connector that can read the voltage(CM) and while the car is running with the A/C on the voltage is at 13.4, when the A/C is off the voltage is at 13.4 but then as soon as the light comes on it drops immediately to 12.4ish.

Any ideas on why this is doing it would be greatly appreciated!

ezone

No clue here, doesn't sound familiar.
Voltage dropping off when the battery light comes on looks like alternator quits charging.

Any recent work prior to this problem surfacing? (always a good place to check)

Got any fault codes stored?

A couple places to inspect might be.....battery terminal connections, and battery/chassis/drivetrain ground cable connections.

Monitor battery/charging voltage and try wiggling wire harnesses in the engine compartment, especially the harnesses that have to flex as the engine rocks back and forth (between drivetrain and body). If you happen to see voltage change as you wiggle wires, you found something to pursue.

You could be monitoring terminal voltages on each of the 4 wires in the alternator harness plug to see if one is changing drastically when you get on and off the gas (or if you can make it act up just shifting from neutral to a gear, that makes it easy). If you can find a single wire changing that at least could be a starting point to tracing down a problem.

jmherman1993

Well I bought the car last saturday and this didn't come up during the test drive, of course, why would it. Since then all the work I have done is cleaning and deodorizing since it used to belong to a smoker, fyi Biocide Auto Shocker is fantastic. Yeseterday I had the dash apart and cleaned the inside of the plastic in front of the tack and lights. The only thing I did today before it started doing this was wash the engine bay with citrus de-greaser and low pressure hose. The negative battery terminal looks fantastic but the positive battery terminal looks a little rough.

There also are NO fault codes stored.

What is weird is that the voltage stays the same when the A/C is on and nothing happens like it does when the A/C is off.

ezone

Follow the battery neg cable to the body....I can see it from here, it looks like hell. LOL





My pic, not yours. They do tend to get kinda nasty here, and the other ground cable in the pic leads to the top of the transmission.

jmherman1993

Thank you for the picture! I found the grounding cable and it is clean, in good condition and very firmly attached. The ground cable from the engine to chassis is also very firmly connected on both ends. I tried wiggling all the cables and the voltage reading never budged. I had my brother shift from P to R to D and the engine did flex a little but the ground cable barely moved. Then we went on a test drive to see if i could just show it to him and since it is night and dark out, I obviously had to have the headlights on and the light never came on even though I drove the same way I did earlier. Had the A/C off and it never came on.

ezone

AC on and it's ok?
Headlights on and it's ok?

What happens if you just run the blower fan on full blast without the AC on?



Do whatever it takes to get the battery warning light to come on and stay on without driving the car (engine running of course)...Unplug the 4 wire connector from the alternator and see if the warning light goes out.

jmherman1993

I will give that a try tomorrow when I dont have to use my headlights to drive it.

jmherman1993

Well just tried it and the whole way from my house to cvs, about 2 miles the light never came on. Leaving cvs heading home the light comes on and then as soon as i turn the blower fan on the light goes off. Turned the fan off light comes on, turn head lights on, light goes off.

ezone

ELD causes it to charge at high-rate ok, but the low-rate isn't working....

It might need an alternator.

Try this check to verify the warning light is being turned on (controlled) by the alternator, not by the PCM or gauge module or some other control unit:

Do whatever it takes to get the battery warning light to come on and stay on without driving the car (engine running of course)...Unplug the 4 wire connector from the alternator and see if the warning light goes out.

jmherman1993

I have gotten the light to come on while sitting still in drive with my foot on the brake. However since there is only one of me and I didn't have anyone to help me today I obviously couldn't get the 4 wire plug pulled. But now that I know that I can get the light on while sitting still I am going to have my brother help me tomorrow.

If I am understanding correctly, if the light goes off as soon as the plug is pulled does that mean the alternator is bad?

Another question, what does it mean if the light stays on after the plug is pulled?

ezone

That's what I'm thinking.

There are several items that can control the warning light.

If the alternator is the only unit telling the light to be on, then unplugging it should turn the warning light off. (In theory.)

If another unit is telling the light to stay on, then unplugging the alternator harness wouldn't turn the light off.

My issue is...I haven't tried this on anything newer than 7th gen civic. I'm just expecting the 8th gen will act the same way as the older cars do.

jmherman1993

Ok, so i was able to get the light on ehile tunning and stopped and my brother unplugged the 4 wire plug and the light went off, then as soon as he plugged it back in it came back on. So based on what you are saying the alternator is probably going bad. What he is suggesting is to look into replace the voltage regulator because that should be cheaper.

Does that sound right?

ezone

I'd just toss an alternator at it.

Can you buy a regulator easily, or any other guts of the alternator? Can you get the alternator split apart to replace those guts?

Do you have a starter-alternator rebuilder near you?

jmherman1993

My mechanic brother-in-law told me that there is a place that rebuilds alternators in a town I drive past everyday on the way to work. He had one rebuilt there and he said they did pretty good with it. And for less than a new one, it sounds like a good idea to me.

ezone

We used to have two rebuilders in my town, one great and one ...less than great.
The great one retired and closed shop.

The other one rebuilds using the cheapest parts he can get, and the quality really shows up later on. I refuse to use that place.

Best of luck to you.

jmherman1993

If I were to buy a new one, what brand do you suggest? I dont need anything spectacular because everything is stock.

ezone

I work for a Honda dealer.
Take a guess.

CraigW

iTrader: (1)

Use a rebuilder, or ask dealer about factory rebuilt/reman unit.

jmherman1993

Well it has been a couple weeks since I replaced the alternator and the light has not come back, so I would say problem solved! Thanks for the help ezone!

ezone