trhs75

I notice at idle and when driving that my lights flicker or pulse a little bit. The dealer couldn't see anything wrong. I suspected a bad alternator or something. All the exterior lights do this together, and it doesn't seem to relate to engine speed. If it's occurring in the dash lights, I haven't noticed it. Anybody ever have this problem?

salimshah

I dont think this is problem. The alternator output varies with load and rpm (you may not feel it but the ecu keeps regulating engine idle rpm). I would call it a failure if the alternator fails to charge up the battery.

If the flicker bothers you a whole lot, you can investigate/invest in a grounding kit and capacitor. [although not needed]

Salim

bob2200

I haven't noticed this on my RX. It could possibly be the battery, or the cables or clamps associated with the battery. If the battery is more than 5 years old, I'd replace it. (Or you just might have a more critical eye than I do).

You could try measuring the voltage at one of the cigarette lighter receptables. When the engine is running, it should be close to 13.6 volts. The alternator, in conjunction with the voltage regulator, should maintain this voltage pretty closely when the engine is running. The 12 volts is when the engine isn't running. The battery is what smooths the pulsating DC coming from the alternator into constant DC. It acts like a capacitor in this situation. That's why I mention the battery and the associated wiring.

bob2200

Another possibility is a bad diode in the Alternator. The dealership should have discovered this. A good auto electrical shop should be able to test for this. This would make the pulsating DC from the alternator even more pulsating.

bloo1987

actually this happens to me too. unfortunately its not when im idle its when my sub knocks. everytime the sub knocks my tail lights pulse. so i would like to fix this too.

salimshah

Alternator produces more than 12v. The battery gets charged with voltage in excess of its standing voltage (typically 12v). The battery acts as a clamp on voltage and acts like a big capacitor (holds voltage and provide extra current as much it is capable of doing).

The wires although good conductors present some resistance and that is where the loss in power happens. If you put excessive demand of current the capacitor action holds the voltage at the battery and the loss due to resistance in wires produce a voltage drop (which you see in loss of light intensity).

So here are your options ... improve the wires (thicker wires). Bring the battery closer to the amp (shorter wires). Add a large capacitor near the amp [This should be done with some current limiter as the capacitor wants to keep 0v when you switch on].

I hope this explains why you have lights dim when you have heavy current demand [A lot less efficient Amp design uses constant current demand output stage (class A, ClassB, and class AB type) .. but they draw constant current when there is no-sound].


For the first post where flicker is present idle .. it has more to do with alternator producing varying voltage and also presenting varying load to the engine.

Salim

Lil4X

I'd check the voltage across the battery terminals with the engine idling when this occurs. If as Salim said, the battery is going away, unable to perform as a "reservoir" for the system, you should see a voltage below 13.8v. If you are using a digital multimeter, you should see the flicker expressed as a rapid voltage variation as well. If the lights still flicker with the engine off, and your entertainment system off, you probably have another set of problems altogether.

The RX 300 and 330 both have engines that crank relatively easily, so despite a pretty badly deteriorated battery, the engine will seem to crank normally. If the alternator is unable to maintain the battery charge, you may have a bad alternator (probably diodes) or a battery that has shorted internally. The latter case usually is made evident by the battery running down without the car being driven. The usual failure mode of a battery is a single cell (there are 6 2-volt cells) shorting - the plates collapsing on one another, rendering that cell useless.

trhs75

I appreciate everyone's help. I'll try checking things out when it when I get some time. I'll let you know what I find out. Thanks!!

miniround

...what if you notice that your headlights dim for the second you open and close your windows?

salimshah

Most common analogy for electrical stuff is what you observe in water distribution.

Think of each load as a faucet.

When one is running and some one opens another faucet, you observe change in flow at the first.

Nothing is wrong, unless your battery is draining more than it is being charged. [Rest easy].

Salim

trhs75

Makes sense. Good analogy!

atlbrent

New to this forum and have already found loads of information! I am experiencing this same issue and it has baffled me so far. Hate to revive an old thread but thought it better to do so rather than starting a new one. Anyone have any success fixing this or finding the culprit?

Thanks

bob2200

Brent,

Welcome to Club Lexus. Which of the many symptoms in the thread do you have? Original battery? Do you have a voltmeter to measure the voltage?

trhs75

Brent, I noticed it got a LOT better when I replaced my aging battery. I wouldn't have replaced it just for the pulsing, but the battery finally died altogether. Good luck!