Hedlight Brightness Fluctuates up and down
Thread Starter
Vroom Vroom..!
Joined: May 2002
Posts: 116
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Hedlight Brightness Fluctuates up and down
Anyone knows the reason why the headlights brightness dims down and go back to bright while the car is in idle?
Almost looks like the power to the headlights goes up and down while standing still,
BTW when I press the gas the intensity/brightness increases, and after a while of being standing still on idle it will start fluctuating up and down again
Almost looks like the power to the headlights goes up and down while standing still,
BTW when I press the gas the intensity/brightness increases, and after a while of being standing still on idle it will start fluctuating up and down again
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Joined: Jun 2002
Posts: 473
Likes: 0
From: Cincinnati Ohio
When something like your a/c or fan in your engine turns on, that will usually cause it to do that to my car. Its just doing it because power is being drawn from your battery. It happens to me if I leave my car running and the engine starts to get hot, then the fan kicks on and power is drawn from the battery and the lights will dim for a second or so. I would say that you are going through the same deal? It happens at idle to me too.
Senior Member
Joined: Apr 2001
Posts: 8,232
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From: Concord, NC
Your alternator could possibly be going bad as well and not charging the battery like it should. Try running some diagnostic checks on the battery/alternator to find out if one or the other is failing.
Get a voltmeter and measure the voltage across the battery terminals. Make sure you're measuring on DC scale. Ideal range is 14 volts but if you read lower than 12, it's probably the alternator. Don't worry about what's below if that's the case.
If it is still reading around 14, try turning everything on that requires power like heater, rear defroster, radio, lights, etc. and give the car some gas (in neutral). Have a buddy measure those terminals again. Voltage should still be around 14, but if lower than 13, this is again an indicator of a bad alternator.
Also, there's another step that I found quoted from another site:
Hope that helps..
Get a voltmeter and measure the voltage across the battery terminals. Make sure you're measuring on DC scale. Ideal range is 14 volts but if you read lower than 12, it's probably the alternator. Don't worry about what's below if that's the case.
If it is still reading around 14, try turning everything on that requires power like heater, rear defroster, radio, lights, etc. and give the car some gas (in neutral). Have a buddy measure those terminals again. Voltage should still be around 14, but if lower than 13, this is again an indicator of a bad alternator.
Also, there's another step that I found quoted from another site:
One last failure mode is of course noise. The rotor inside the alternator rotates on bearings, normally very high precision needle bearings, and these can fail. When they do you will hear a loud grinding noise associated with the alternator. To isolate the noise take a length of tubing, heater hose will do fine, put one end to your ear and move the other around in the vicinity of the alternator. The noise will be much louder when you point it at the alternator if that is the culprit. Other possibilities are the water pump and the power steering pump which are also driven by the engine belt. To further isolate the noise disconnect the drive belt and spin the alternator by hand. If you hear a rumble or grinding noise then the bearings are shot. If you don't hear a noise the problem may still be in the alternator since the bearing might be quiet without the loading of the drive belt tension. Check for side play in the pulley. If you are pretty certain the noise came from the alternator it is a relatively simple task to take it apart and visually inspect the bearings, else swap it in for a rebuilt. Your auto supply store will normally bench test the alternator free of charge and can tell you at that time if the bearings are noisy.
I like integra's
Joined: Feb 2003
Posts: 714
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From: Pittsburgh, PA
My last car did that and I got a new battery and it solved everything. If you go to Advance, they can test both your battery and alternator for free, except make sure you get a more knowlegable employee, I had a lady do mine once and she was saying the opposite of what was going on becuase she couldn't read the tester right.
