On 9 Dec 2005 14:33:05 -0800, polymorph@polyphoto.com wrote:

>1991 Honda Accord LX, 2200cc engine, 4 door sedan with standard
>transmission.
>
>The charge light came on one day, went on and off again, finally came
>on and stayed on.
>
>Frustrating... after checking all the wiring, removing and retightening
>the battery cables and the wires on the alternator, checking ground,
>the light went out. Thought I'd fixed it. In the time it took to pack
>up all my tools, went back and started it and the light was on again.
>
>Removed the alternator and battery and had them tested at the local
>parts store. Both test good.
>
>Rechecked everything, I see on the wiring diagram there are a couple of
>wires that go to the Engine Control Unit/Module, so I take the ECU out
>and clean it's connectors by taking them off and on again a few times.
>Charge light goes out again. I shut off the car and restart 3 times
>(letting it sit a few minutes between), light goes out immediately when
>engine starts as it has when things were fine.
>
>Nope, restart car about 10 minutes later and the charge light is on
>again. No wiggling of wires or tapping on anything makes it change.
>
>I even took out the ECU and resoldered all questionable solder joints
>(I've been an electronics tech for a number of years). Charge light
>still on.
>
>During one of the times when it was working, I took some readings. I
>doin't know how meaningful they are except they tell me that it is not
>a wiring problem between the alternator and the battery.
>
>The only difference between charging and not, one of the two wires
>between the ECU and alternator: normal operation, when first started it
>is about 3.6V, dropping to about 2.5V. Later starting it and the charge
>light comes on, the same line is now about 1.5V.
>
>But without knowing which way this signal goes, I don't know if the
>fault is the alternator or the ECU telling it the wrong thing.
>
>I see some mentions here of worn out brushes. Where might I find those
>in the northwest USA? I've checked a few places like Autozone and it
>lists them but says unavailable.
>
>Thanks,
>Steve


I would guess that the brush set in your alternator is at the end of
the service life. As a brush gets so short that it cannot make
constant and continuous contact with the commutator (or whatever they
call the rotating contact surface in an alternator), it will give an
intermittant failure signal. often times you can tap the alternator
and temporarily reseat. Therefore the good reading when the
alternator was fooled with to test.

Change the brush set or change the alternator if other things wrong
(bearings)