I agree with your procedure, but would like to add a few things. Some
Hondas have a system where the ECU can change the set voltage for the
voltage regulator. Under certain circumstances (warm engine, low
electrical load etc.) the ECU will call for lower voltage at idle. This
can be defeated by stepping on the brake. So to avoid erroneous
readings, step on the brake while doing the voltage measurements. I
don't know when Honda started using this system, but I know my '94 has
it.

Also, I doubt 13.7 is the right value. The spec. for the '87 Civic and
also the '94 Civic is 14.5 V +/- 0.6 V measured at the battery with no
electrical accessories turned on (pr. Helms service manual).


Charlie S wrote:
>
> When your lights go bright and the fan speeds up etc. that means the
> voltage has gone up above normal.
> First thing I would do is check the voltage. Put a voltmeter on the
> battery terminals. A fully charged battery should show 12.7 volts. Now
> turn the engine on and read the voltage on the battery terminals. It
> should now read about 13.7 volts. Have someone change the speed on the
> engine and watch the voltmeter....if the alternator is good it should
> not change voltage.
> Alternators produce an alternating current(AC), have a rectifer
> circuit in them to produce a DC current and a built-in regulator to
> give a 13.7 volt DC output.
> I am going to guess you have a bad alternator.
>
> Find a mechanic that understands electrical, not all mechanics
> understand electrical problems.
>
> I looked a 1990 "Accord" wiring diagram and it shows two wires from
> the alternator to the "engine control module'. I have no idea what
> that is for.
>
> Cheers, Charlie
>
> On 26 Dec 2003 16:13:33 -0800, xbiggwbx@aol.com (Wayne) wrote:
>
> >Hello!
> >I own a 1990 Honda Civic, 4-door/4 cylinder car. When driving, I
> >noticed that my headlights and dash board lights get very bright, and
> >then dims back to normal. At the same time this happens, my defroster
> >fan motor, speeds up and then slows down to normal in conjuction with
> >the headlight and dashboard lights.
> >
> >I also notice that my battery light on my dash board flickers on and
> >off occasionally apart form the dash board lights.
> >
> >
> >Oh by the way,
> >
> >My alternator was replaced March of 2003. Prior to changing my
> >alternator, my battery light constantly stayed on.
> >
> >My mechanic recently checked my fan belt and told me that it was o.k.
> >
> >Does anyone have a solution to what this problem might be?
> >
> >
> >Please email me: xbiggwbx@aol.com