Lights flickering

[mckrishes]

Hello. I have a 1999 civic with d16y7 engine. The head lights, tail lights, interior dome lights
Are pulsating. This seems to be more prominent when the car is parked and less noticeable when driving at highway speeds. No other problems. The car starts fine.

Topic

[John B Kobberstad]

You should start with a schematic. http://www.bbbind.com/tech_database.html

[John B Kobberstad]

Look for a point they may all have in common, ex. a common ground

[mckrishes]

Ok will look a the diagrams. Also the dash lights pulsate as well, but the lights for the radio, ac knobs, etc seem to be unaffected. And the pulsing seems to be prominent when slowing down. Where is the first place I should start?

[Buggsy]

Sounds like the rectifier on the alternator. I’m not sure how to test that on the car. Maye you can measure the voltage output from the alternator while someone revs the engine. On old cars, I’d say unhook the alternator and run the car off the battery, but I’m not sure that’s valid or safe for modern cars.

[mckrishes]

Some updates. I followed Eric’s video. I tested the battery and the reading was around 12.47. I started the car and increased the rpm’s and the battery voltage did not seem to change at all. Maybe a about a tenth of a point or so. I turned off the car and waited a few minutes and started the process all over again.

I checked the battery and the reading was about 12.6. Started the car and increased the rpm’s and got a reading of around 13.5 to 14.0 and never passing 15.5. I turned on all the accessories and started the car and got good readings of 13.2 to 13.5. I also tested the resistance of the cables as Eric described and my reading was 0.0. I also inspected the lights around the car and everything is working properly. No flickering at all.

I find it strange that during my first test, the voltage didn’t increase, but during my second test, everything seemed to be fine. What could this indicate? I have not tested the battery with a load tester yet. I’ll need to go to an auto parts store for that since I don’t have a load tester.

[twiggy]

Try measuring the battery voltage in AC mode on your meter, with the car running. This is a new idea for me, I just measured my car in AC mode and read less than 0.1V RMS. If you have a bad rectifier, than I would expect the AC voltage to be much higher. Of course a scope is best but few have those around.

[mckrishes]

I measured the volts in AC mode before starting at 28 and after starting at 31. I performed the test again in Eric’s video and got good readings. Also, I inspected all my connections and they appear to be intact.

What is a rectifier?

[twiggy]

By 28 and 31 I assume you mean mV ? Then that it ok. The alternator outputs an AC voltage and the rectifier (or rectifier network) is another name for diode, which converts the AC voltage into a rough DC voltage which is really a rectified sine wave. Then the regulator smooths everything out to a pure DC voltage.

This is a rough test measuring AC with DMM but if either the rectifier or regulator were to fail, then I would expect the DC to the battery to show AC voltage meaning that the DC voltage is varying over time.

Your first test when your car was idling and you measured 12.47V is suspect to me. This means that, at that time, your alternator/regulator appeared not to be working at all. This could be caused by the belt slipping so that the alternator wasn’t spinning enough or that the alternator is intermittently bad.

Try checking the brushes on the alternator.

[mckrishes]

Ok. I will check the brushes on the alternator and re-check all other connections. The belt was recently replaced, but I will check that as well.

If this was a regulator/rectifier problem or an alternator issue, is it possible for both to work intermittently or do they just have a tendency to fail outright?

[twiggy]

The brushes could cause intermittent failure. Semiconductors such as regulators and rectifiers can also appear to fail intermittently but usually temperature changes can bring out a failure. If semiconductors parts are mechanically damaged, they can also fail as they are subjected to vibration and/or temp changes.

[college man]

heres a couple videos

[mckrishes]

Thanks collegeman. I did watch all the videos and performed all the tests
except the battery load test. I will have to go to parts store for that. All connections were checked. The only finding so far was the alternator did not appear to be charging on my first test, but when I repeated the test, everything was fine. I’ll keep you updated.

[EricTheCarGuy]

One more place to look might be the ignition switch. I’ve seen this in the past where the switch would go bad and it would be like shutting off the car. Try wiggling the ignition key while the engine is running, if it stalls or you see the symptom replace the electrical portion of the ignition switch and recheck for the symptom.

http://www.ebay.com/itm/92-93-94-95-Honda-Civic-Ignition-Switch-Wiring-NEW-/300318496717?hash=item45ec6097cd&item=300318496717&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

[mckrishes]

I have some new information. I haven’t started the car in about a day or so. I checked the battery and it reads 12.43. I started the car and the meter reads about 13.2. I waited a few minutes before putting a load on the alternator and I still had consistent readings of 13.2 to 13.4. When I applied the load (turned on a/c, defrost, wiper blades, etc.), the voltage started going up and down from 13.4 to 13.2 to 12.9 to 13.1, 13.2, and so forth. At one point, it jumped down to 5.0, then back up to 13.2, back down to 10.0. That didn’t happen often, but I noticed it. When I increased the rpm, the voltage increased and stayed consistent at around 13.2 to 13.4. Of note, the flickering of my lights did not occur until I applied the load. I still need to do the load test on the battery. I know that if the voltage drops with a load on that the alternator is suspect, but I am getting various readings. And if I increase the rpm’s, the problem goes away. I checked the belts and connections again and they are good. I inspected the pulley and it was spinning and intact. I didn’t check the brushes because I can’t really get a good look inside the alternator, but I will try again later.

I forgot to add. I did wiggle the ignition key as Eric suggested and it didn’t do anything, so that’s when I re-checked everything

[mckrishes]

O.k. I went to the local auto parts store and load tested the battery. It tested good. They also tested the alternator and said it was good (But they did not test it under load). Afterwards, I retested the system again. I tested the alternator (following Eric’s video). My initial battery reading prior to starting was 12.6 volts. Then after starting and placing under load, I received readings of 12.5 to 12.8. When I accelerate the engine (under load), I receive readings of 13.5 to 14.0.

I watched both of Eric’s videos on alternating testing. One video uses a battery load test (he does not use the load tester to place the system under load), and in that video, he says anything above 12 volts is good. In the other video he uses a multimeter (which is the procedure I followed), and he state’s that if the voltage is not over 0.5 volts above the baseline (not under load), then the alternator is not good.

So far I am thinking that my alternator is functioning, but not properly. It seems like the alternator functions properly at anytime except when it is under load at idle. With the lights flickering, I suspect either a regulator problem in the alternator (there is no external regulator that I am aware) or an ECU problem. I have not tested the ECU yet and I am thinking this should be my next step.

Any suggestions or advice would be greatly appreciated. Thanks.

[Author]

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