Slicer1989

I have a 99 1.6L Auto 4 door Civic... and the battery light is on. The alternator seems to be putting out the correct volts, The battery cranks the car just fine - The P/O said the alternator was replaced and the light is still on. There doesn't seem to be any electrical issues, so I Was wondering what might cause this issue?


Also, Every now and then the transmission will shift pretty hard, Especially if I am, Let's say... Coming into an intersection and the light just turned green, if I am still moving and give it gas, it will sometimes slam into gear... Under normal operation, it seems to shift pretty smooth and no shudder / slipping that I can tell. I was thinking about changing fluid / filter... but with 221k I am a little worried it might make the transmission worse. The fluid doesn't smelled burned, but it's definitely dark. (Not super dark)

ezone

Unplug the 4 wire connector from the alternator and see if the battery light turns off.


Change trans fluid ASAP. Simple drain and fill. Do not use chemicals or a machine.

If you want to flush it all, you could buy a case of fluid and do multiple drain/fill as per Hondas trans fluid service recommendations

Each drain and fill will take about 2.5 quarts

Make sure you have a funnel that will reach the trans dipstick hole before you begin.
I'd use Hondas ATF DW-1, but that's me.

Slicer1989

I'd never use a machine to flush a transmission, I'll do a few drain and fills and see if that helps.

What does unplugging that connection do? I'll check tomorrow when it's light.

ezone

It's my diagnostic step #1 to see if the alternator has control of the light, or if something else is keeping the light on.

Slicer1989

I never tried disconnecting that plug, but I took it to two different places, and the battery, starting and charging system all passed 100%.... The light isn't 100% bright, during the day I can barely see it on, and at night it isn't super bright, but more noticeable.

ezone

The alternator can be bad and still charge.
First you need to figure out if the alternator is the item keeping the warning light on.

Unplug the harness...if the warning light goes out then the voltage regulator is faulty (assuming nobody hacked the wiring together incorrectly).
If the light stays on then you need more investigation.

Slicer1989

Unplugged the cable on there, and the light went out.

ezone

You checked this with the engine running, yes?
Alternator internal fault (voltage regulator can't turn the light off).
Replace alternator.

See if previous owner who replaced it got a warranty with that.

Slicer1989

Yes, With the engine running... Even shut down the car and restarted it, Light stayed out until I reconnected it.

Doesn't really look like the alternator was replaced, or if it was... It was with a junkyard one.