Hey everyone,
I have a '92 Civic Hatchback with the 1.5L and a manual tranny.

I am having an issue with my charging system, well, it is simply that the alternator never turns on. It sits at 11.7 - 12.2vdc all the time. It never goes up, and sometimes I lose the alternator all together and it drops down to around 10vdc and continues to die.

This issue has already killed 1 battery, and I am afraid that if I let it continue, especially with winter coming up it will destroy another.

I have replaced the fuse box in an effort to get a good charging system sensor that is inside the box itself, and the problem persists.

I think that if somebody can identify what the wires on the alternator plug all do exactly I will have better luck tracking down the problem.

Thanks for any advice you can give!

 

Here's what the wires do:


Big single terminal - The output from the alternator to the battery. I think the charge voltage is sensed there. If you don't have a solid path to the battery, the alternator may be running normally but it isn't reaching the battery.
"IG" - This wire powers the regulator, it comes from the ignition switch and has battery voltage all the time the key is on.
"L" - This wire drives the battery icon warning light on the dashboard. The alternator grounds it to turn the light on. The other end of the light bulb is powered from the same circuit that powers the "IG" wire.
"FI" - This wire is an output from the alternator to the ECU. It tells the ECU how hard the alternator is working, the ECU uses that to stabilize the idle and maybe activate the C wire.
"C" - This wire is an input to the alternator from the ECU. When the ECU grounds the wire, the alternator output is reduced to about 12.0 volts. That lightens the load on the engine. The ECU should only do that at wide open throttle or if the idle is abnormally low (to prevent stalling, the ECU tries to shed load such as the A/C and I assume the alternator).

So offhand it sounds like your problem is related to the C wire, though it could also be lack of power to the IG wire.

 

wow, that is exactly what I needed to know to do some more testing! Thanks a lot!

 

I appreciate the help and I found out a little more about my alternator charging system.
I have 4 wires on the green plug on the alternator:
Black/White
White/Black
Blue
White/Yellow

I found that the black/white wire is what you called "IG". It has ignition voltage only.
The White/Black wire is what you called "L". It turns on the battery indicator when grounded.

The blue wire always seems to have 5vdc with the ignition on, and the White/Yellow has 5.8vdc with the ignition on.

 

Where did you get the wire labels? On the green plug on mine, there are no labels.

 

Maybe you just need a new alternator..

 

No the alternator is not bad. I replaced it a month ago, and then last week I had a shop looking into my charging system issue pull it and test it and it still tests good.

They gave the blame to the charging circuit switch in the fuse box so I replaced it. It did not solve the problem.