Honda Car Forum

Whenever the alternator of my '98 Accord sedan gets an additional load put
on it, the headlights of the car temporarily dim to some degree. This
additional loading seems to take place whenever I turn on the rear window
defogger, A/C, or fan. The alternator belt isn't very old at all and it
isn't loose either, so I am suspecting that the alternator itself could be
on its last leg.

Other than the alternator belt or alternator itself mentioned above, is
there anything else that could be causing this dimming of the headlights
whenever HVAC controls are turned on?

Thanks in advance for any help/advice that you may have to offer me on this
one.

Ron M.

Ron M. wrote:
> Whenever the alternator of my '98 Accord sedan gets an additional load put
> on it, the headlights of the car temporarily dim to some degree. This
> additional loading seems to take place whenever I turn on the rear window
> defogger, A/C, or fan. The alternator belt isn't very old at all and it
> isn't loose either, so I am suspecting that the alternator itself could be
> on its last leg.
>
> Other than the alternator belt or alternator itself mentioned above, is
> there anything else that could be causing this dimming of the headlights
> whenever HVAC controls are turned on?
>
> Thanks in advance for any help/advice that you may have to offer me on this
> one.
>
> Ron M.
>
>
if you're talking about with the motor at idle, it's normal. all cars
do it. look at the power output of an alternator vs. rpm's.

My recollection is this is perfectly normal. With the headlights on and the
car cruising, adding further load (like defogger, A/C, interior fan) will
lower the voltage at the alternator's regulator, and so dim the lights.

For reinforcement of this, see the service manual page for testing 1995-97
Civic's charging system, at the link below. Note that the voltage "checks
sat" if, with the engine running and the headlights on, and then the
interior fan and defogger is added, it drops from over about 13.6 V to under
13 V.

http://media.honda.co.uk/car/owner/m...pdf/23-a96.pdf

"Ron M." <nobody@nowhere.net> wrote
> Whenever the alternator of my '98 Accord sedan gets an additional load put
> on it, the headlights of the car temporarily dim to some degree. This
> additional loading seems to take place whenever I turn on the rear window
> defogger, A/C, or fan. The alternator belt isn't very old at all and it
> isn't loose either, so I am suspecting that the alternator itself could be
> on its last leg.
>
> Other than the alternator belt or alternator itself mentioned above, is
> there anything else that could be causing this dimming of the headlights
> whenever HVAC controls are turned on?
>
> Thanks in advance for any help/advice that you may have to offer me on
> this one.

"Ron M." <nobody@nowhere.net> wrote in
news:sLdGf.19382$%84.1663@tornado.southeast.rr.com :

> Whenever the alternator of my '98 Accord sedan gets an additional load
> put on it, the headlights of the car temporarily dim to some degree.
> This additional loading seems to take place whenever I turn on the
> rear window defogger, A/C, or fan. The alternator belt isn't very old
> at all and it isn't loose either, so I am suspecting that the
> alternator itself could be on its last leg.



Some dimming at idle is normal, as jim says.

If there's excessive dimming until you rev it, it's a battery thing, not an
alternator thing. Make sure the battery measures 12.65V with the engine
off.


>
> Other than the alternator belt or alternator itself mentioned above,
> is there anything else that could be causing this dimming of the
> headlights whenever HVAC controls are turned on?



Possibly the Electrical Load Detector going bad?



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

"TeGGeR®" <tegger@tegger.c0m> wrote in message
news:Xns97648769CE74tegger@207.14.113.17...
> "Ron M." <nobody@nowhere.net> wrote in
> news:sLdGf.19382$%84.1663@tornado.southeast.rr.com :
>
>> Whenever the alternator of my '98 Accord sedan gets an additional load
>> put on it, the headlights of the car temporarily dim to some degree.
>> This additional loading seems to take place whenever I turn on the
>> rear window defogger, A/C, or fan. The alternator belt isn't very old
>> at all and it isn't loose either, so I am suspecting that the
>> alternator itself could be on its last leg.
>
>
> Some dimming at idle is normal, as jim says.
>
> If there's excessive dimming until you rev it, it's a battery thing, not
> an
> alternator thing. Make sure the battery measures 12.65V with the engine
> off.
>
>
>> Other than the alternator belt or alternator itself mentioned above,
>> is there anything else that could be causing this dimming of the
>> headlights whenever HVAC controls are turned on?
>
>
> Possibly the Electrical Load Detector going bad?
> --
> TeGGeR®
>
> The Unofficial Honda/Acura FAQ
> www.tegger.com/hondafaq/

Thanks for all of the responses. Based upon the responses that I received to
my original post,
I probably shouldn't be too concerned about this issue since the dimming
effect is minimal and for an extremely short time duration. The reason I
inquired about this issue is because no other vehicle that I have owned
since 1977 has ever exhibited this same type of behavior. Not a single one.
I purchased this car used on Dec. 28th, 2005 and really do like it a lot so
far. This slight, temporary dimming of the headlights has pretty much been
my only concern with this used car to date.

Once again, I appreciate the info!

Best regards,

Ron M.