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Re: Lights go dim Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 7 Mar 2002 09:52:12
In Reply to: Lights go dim, Russ, Wed, 6 Mar 2002 23:29:50 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The voltage in the display is averaged over a second or so. If you get a big drop in voltage (say down to 12 or 11 or even lower) for a tenth of a second or so, you'll only see a small drop on the display. The lights, however respond much quicker. Basically, what Steve said.
Something is pulling the voltage down, but only for a brief time. The possiblities are an intermittent short circuit, which I doubt, or a transient load. The transient load that comes to mind is the AC compressor clutch. The clutch is a big current hog when it first pulls in. The ACC system runs the AC even in cold weather (at least over 32 F) to defrost the windows.
Run an experiment. On some above freezing day, let the car idle with the hood open. Set the ACC to Defrost, and watch the headlights and the AC compressor clutch. Is there a correlation between when the AC clutch pulls in and the lights dim?
If so, then you've found the problem, but not necessarily the source. You might have a AC clutch that pulls a lot of current. But before I worried about that, I would inspect the battery clamps and wires. Make sure the connections are clean - that involves removing the clamps and cleaning the mating surfaces. Inspect the wires for signs of corrosion - white or green powder between the copper strands in the wire. Make sure the connection from the battery negative to the chassis is good.
The alternator provides the current requirements for the car when the engine is running, but the battery can make up for large transient loads. A bad battery connection means it can't supply the current well.
Yes, it may just be a quirk of your car. I know it isn't in any of mine. But it also might be the first warning sign of a problem. Now would be a good time to check it out, before it shows up big time in the middle of the night on a back road somewhere.
Good luck!
posted by 140.157....
, Thu, 7 Mar 2002 09:52:12 <-- Viewing This Message
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