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Dimming lights... could it be the alternator?

Old 01-08-2010, 07:54 PM
Thread Starter
Join Date: Oct 2008
Location: Clatskanie, OR
Posts: 73
Default Dimming lights... could it be the alternator?

Around the same time my fuel pump was going out (Nov. 08) I noticed my headlights would randomly dim along with the gauges. I asked the dealer and he said the "charging system" only kicks in when necessary so I continued on. Recently, the lights are dimming a lot more often and they are getting a lot more dim and staying that way for about five or so minutes. It is really drastic when my stereo is playing a little louder as well. So this made me think that I was drawing more power than the alternator, battery, or something else could keep up with. Any ideas? Thanks in advance and sorry for the longer post.
Old 01-10-2010, 10:03 AM
Junior Member
Join Date: Jan 2010
Posts: 3
Question Have you added anything about the same time this started?

Have you added anything about the same time this started? Like a amp, new stereo system or something like that? The main reason lights dim are do to a large draw on the charging system. If you have remove the fuse for that item and see if you notice them dimming any more. If you have not take the car to a shop that specializes in electrical repairs otherwise you can rack up a lot of billable hours tiring to find the problem. I don't think it is the alt because the lights dim on and off, however if you take it to an electrical they will check it out it could be alt or regulator going bad but they will need to duplicate the condition to be sure.

I have a Diesel pick up and in cold weather after I start it the lights dim about four to ten times and very noticeably. It is do to the intake and fuel heaters cycling on and off to per heat the air going into the engine and to keep the fuel from gelling in cold weather.


Last edited by dtropnevad05; 01-10-2010 at 10:09 AM.
Old 01-15-2010, 08:57 AM
Senior Member
Join Date: Mar 2008
Posts: 285

Sounds like maybe a Voltage Regulator...However, take your car to O'Reilly Automotive or Auto Zone...they can check your alternator for free.

It's real easy to check it yourself though if you have a Volt Meter...just hook it up to your battery and turn on the engine..rev it up...if the voltage goes up when you rev it up...your alternator should be fine.

Also, check your make sure it is taking a charge..Auto Zone or O'Reilly can check this to. Good Luck and Happy Motoring...
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