Flickering lights, and battery wont stay charged

[Vinny]

Hello Everyone,

I have a 2001 Toyota Avalon, and my problem consists of the lights flickering and the battery wont stay charged. I’m suspecting its the alternator, and even pulled it out to have it tested in the morning. But the strange thing is that the “Battery Warning Light” isn’t on. Here are the symptoms for my car:

It will start on a jump start and stay running, but the lights are flickering. If I put a large electrical load on the car (for example roll down all four windows), the car will stall. What are your thought ETCG community?

The flickering gets worse when I rev the engine! (Not higher frequency, but larger light to dark transitions)

Topic

[dollman0]

I don’t know the electrical system of this particular car but here is an idea
The alternator can put out just enough to keep the charge light off and not put out nearly enough amps to run the car, thats why the power windows kills the engine.

I have an older toyota and the charge light was coming on, I replaced the brush pack and its been going strong for the past five years. It may be the same deal with your alternator, but I don’t know the system.

Try checking the wiring for high resistance such as a bad fuseable link causing your problem. Touch a DMM lead to the alt charge wire and the battery pos to see if there is more than .5v between the alt and battery. A high reading indicates a problem and repeat on the ground side from the alt base to the neg post. If you are getting a low voltage drop in the wiring you have isolated the possibility of something other than the alternator. There is also a control wire that feeds back to the ignition switch, normally a F terminal and it should switch on/off with the key.

All it takes is a bad diode in the alternator to kill the output, it should put out 50 amps at idle and 100A at 2000 rpm. If you can get an amp clamp on the charge wire, you will know how much it is pushing.

I hope this helps you determine the cause of your issue.

[college man]

If you have to jump the car to start it. Have the battery load
tested at an auto part store and replace as necessary.

[Vinny]

Just tested the alternator and it was fine. What I did find odd is that they didn’t test for amperage. I purchased and alternator anyways and they said that if it didn’t fix it I can return it. I also cleaned the battery terminals and couple of the engine ground wires.

[dollman0]

Go back to the voltage drop procedure I mentioned before and I read online that there can be an Alternator Fuse in one of the power distribution boxes (40A 60A 80A 120A etc). Also check for key on/off power on the alternator plug to see if the control circuit is working.

If none of these work, I have no idea because I am not familiar with that particular model of Toyota.

[Vinny]

I just did the test that you mentioned, dollman0, and the positive test came out to 0.112 volts with the engine running and no load; 0.226 volts with AC on high and defrost on. On the negative side it was about 0.05 volts. So this means that its not the alternator, right?

I had to purchase a new battery to perform this test and of course everything is fine with a fresh 12v source. With the car running, the voltage across the battery terminals is 13.8 volts.

Just as a precaution I performed a parasitic load test, and found that to be about 0.02 volts.

I hope its just needs something as simple as a battery. After all, the old one was 5 years old.

[Bill]

It’s possible that both the alternator and battery are bad. I would expect a little higher voltage accross the new battery with the engine running with no load like 14.5V.

[Vinny]

Just redid the voltage test across the battery terminals.

Battery Voltage 12.5 V
Engine idle no Accessories running 14.4 V
Engine idle with radio, AC, defrost, and high beams on, 14.2 V

All of the flickering is gone with new battery installed, but returns when I disconnect the battery with the car at idle.

My intuition is leading me to believe the the alternator is producing enough power, but there may still be an internal problem with the alternator not being able to produce clean DC voltage.

[twiggy]

You should never disconnect the battery while the car is running. The battery serves to stabilize the voltage in addition to supplying power.

The flickering with battery disconnected may be normal and your old battery may have caused flickering due to high internal impedance.

I think you should do nothing more, drive the car and see what happens.

[Osman]

Doesn’t the alternator also have a direct connection to the positive terminal to the battery which can get corrosion? If there is a bad connection won’t it cause these problems? Just something to look at.

[college man]

Thats not a good test to disconnect the battery terminals
while running. All that does is over work the alternator.
The battery must be hand and hand to work.

[Walter Cheryba]

Your old battery may have had one or more shorted or open cells. I’m a latecomer to this issue yet the battery is where I’d put my betting money. 😉

[Bill]

I’m surprised you didn’t blow every light bulb and electronic component that was on at the time you disconnected the battery with the engine running.

That’s an trick with old cars with a generator. They only produced 30dc amps however.

[Vinny]

Thanks wysetech! I didn’t think about that and it was something that was suggested by a friend. Hope I didn’t do any damage! The car is running fine for now. The funny thing is that the lights were always flickering at a cyclical manner (about 5 hz) for the past 2+ years since I’ve owned it. With the new battery, that has gone away.

A did a little search on online and found this explanation on http://www.batteryfaq.org/

9.2.12. Never disconnect a car battery cable from a vehicle with the engine running because the battery acts like a filter for the electrical system. Unfiltered (pulsating DC) electricity sometimes exceeding 40 volts is produced by the alternator and can damage expensive electronic and electrical components such as the emissions computer, audio system, charging system, alarm system, etc.

[Author]

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