Weird headlight flickering

Sometimes when I drive my 2013 Civic Si sedan, the headlights will randomly dim then get brighter, vacillating between bright and dim. I believe it happens to both headlights simultaneously. I don't think it's related to hitting bumps in the road. It happens only when the car has been sitting out in the cold for a while. After I drive for a few minutes, everything is fine. I haven't noticed any other electrical problems or flickering on the dash - all the indicators are steady.

What could it be??

 

My si did the same thing- battery was no good. I have a deep cycle optimum yellow top now, that can go dead 300+ times and still keep working-these cars req a lot of juice to work right and eat battery's.

 

I just checked the battery immediately after driving - 13.2 V.

 

I checked it again after a few hours, and the battery had dropped to 12.8. I suppose that's still "normal". I started it, turned on the headlights, and measured 14.5 while idling. I didn't notice any flickering this time.

I'll check it again in the morning. Hopefully I can get a reading while it's actually flickering.

The only mod is an aftermarket audio system that I installed. About a year ago I measured the amplifier's current draw with everything turned off, and it was only a few milliamps. Maybe I'll pull out its fuse and see if that magically fixes my problem.

Thanks for the help! I had both the battery and alternator replaced just over a year ago. Hopefully there's not some weird (expensive) problem chewing up the electrical system. If I just have a lousy battery and need to get a better one, I can live with that.

 

This morning the battery was at 12.7. I started the car and turned on the headlights. At first it was reading 14.4, but then the headlights started flickering, and the meter was swinging between 12 and 15. At one point it held steady at 11.9 for a few seconds, then resumed vacillating.

The flickering started about when my sound system started playing music, so I turned off the audio, but the lights still flickered. I'll try starting the car with the audio off this evening and see what happens. I'll also stop by Advance Auto and ask them to test the battery.

 

I have just become aware of Honda's "dual mode" charging. Is that potentially an issue?

 

sounds like a weak battery, my car had dim lights sometimes but not all ways.

 

I think you may be right-- given the time frame that you've mentioned, it may be the Dual-Mode kicking in.

The first paragraph in this write-up seems to match up to your symptoms:

https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto_pres

 

I started the car with the audio system turned off, and the lights still flickered. This evening I pulled out the fuse for the audio amplifier's power cable; we'll see what happens in the morning.

I had Advance Auto test the battery. They said it's good.

I've ordered a FlashPro so I can disable "fuel economy alternator control." Regardless of what the issue is, I want my amp getting a consistent voltage.

 

Have you installed a more powerful radio power amp-it may be in the low amp mode but needs to be putting out more juice for your radio power amp-. I would guess the radio is drawing too much power. You could burn something out like that- even wires burning up-very bad. Try leaving the radio off for a while and make sure that amp isn't drawing power even when off. IF you simply set it at high output you run the risk of burning up your alternator or something else-not such a good idea. I installed a power amp once and had nothing but problems.

 

I had Advance Auto test the battery. They said it's good.

I use an aftermarket audio amplifier to drive my front speakers and an 8-inch subwoofer. With the car turned off, the audio amp draws 3.5 milliamps. The amp powers on as soon as I start the car, but if I have audio turned off at the receiver, the amp draws only 0.03 amperes.

The flickering seemed to be substantially less when I pulled out the fuse for my amplifier, so I guess that's a factor. I'd be surprised if the alternator is incapable of keeping up with it; I suspect my amplifier is just confusing the "dual mode" charging, and the computer is telling the alternator to slack off when it shouldn't. My FlashPro arrives tomorrow. I plan to disable dual mode and see what happens. I'm optimistic that both the amp and the headlights will be much happier with constant 14+ volts.

 

your messing with honda and its one picky car. You added a constant power drain, a trickle charger should be put on if your leaving the car off more than 24hrs, this will effect even a brand new battery. I upgraded to a opt yellow top deep cycle that can do dead and come back because its easy to leave a dome light on hitting the battery with a power drain. So far this new battery seems to have totally solved any power problem which was slight. The car should actually be charging at full not slacking off something isn't working, perhaps a short-very likely coming from your power amp. I have a hondata flash pro and going to look at the setting's, but I have no problems. You may solve part of the problem with flash pro but it won't fix a power drain, a trickle charger would when the car is off.

 

i was commenting on this thread in the 9thgencivic forum. i suspect disabling the dual mode will fix your problem but like my car, it could still be a bad battery. i tested mine several times and it passed each time until one day my car wouldnt start and i charged and tested it again and it failed. think i mentioned this in the other thread. when i first got flashpro and had it disabled it would still dip down to 12.3v while driving before i replaced the battery. im also not sure if the battery was the problem or if having the battery disconnected for a week ( im sure a few hours would yield the same results ) making the constant 14v charging possible. i suspect the battery was the problem.

 

The battery that I replaced would have passed auto zone testing-it seems that their tester is junk and I think this is on purpose to delay, so to make warrantee no good. It seems these Honda's eat battery's all the time due to the strain these cars put on the battery's, maybe that duel mode has something to do with it. I am using the opt yellow top deep cycle which matches to cars electrical system much better than a standard lead acid type. Its too soon to know if I am right or not. I also recommend using a trickle charger if the car is sitting more than 2 days.

 

Thanks everyone for your comments and concerns! After disabling "dual mode" with a FlashPro, I get steady voltages of 14.6 to 14.8 V when the car is running. (And no more flickering!) That might be a little high, but after driving for an hour I looked at the battery, and it wasn't hot or anything, so hopefully it's not now overcharging. When the car is off, I read about 13 V at the battery.

Yesterday the car sat out in the cold all day, and it started right up with no problems. Of course, there's still no guarantee that I won't need a new battery sometime soon. I'll let y'all know if anything unexpected happens.

Also, thanks for the recommendation about a trickle charger! I'm not worried about the 0.0035 A killing it overnight, but if I do need to let the car sit for an extended period, I'll try to remember to pull out the fuse for the audio amplifier.

 

there are other draining things, I noticed if the car alarm is on- some juice being lost there. Instead of pulling the fuse-the best thing is a motorcycle trickle charger .750 amp about $20.

 

35 milliamps is an acceptable draw. It shouldn't kill the battery. Glad the flashpro fixed it. I knew I wasn't crazy that the dual mode was causing my flickering too.

 

I bet you have a weak battery and giving it more juice will help, but not fix the problem. The duel mode shouldn't be causing the flickering problem, but a weak battery would. It maybe normal for a slight flicker when the duel mode is changing. The duel mode saves a lot of gas and keeps the battery from over charging. I had the exactly the same problem and the opt yellow deep cycle battery that can go totally dead over 300+ times,$208 totally fix it with the trickle charger keeps the battery 100% fully charged. The car is now 100% + fixed. Honda put a very cheapo battery in the car. I admit my dodge neon does not have a duel mode and doesn't have this battery or flicker problem. The battery in the neon cost $50 and doesn't need a deep cycle battery. The honda needs the best battery you can put in it. So there you have it a cheapo neon beats the honda again but burns a tiny more gas charging the battery.