My 2009 Fit, since I got it brand new off the lot, has always seemed to have an issue with power. The lights flicker, the heater powers down then up every once in a while.. I figured maybe the tiny little lawnmower battery is the reason. Nonetheless for the last 3 years it's worked ok with these issues.

2 years ago, I had a 300W Fosgate Amp installed because I found the bass in the Fit to be seriously lacking, and I went to a car audio shop hoping for a professional installation, which I'm hoping they did. Looks like they wired directly to the battery, and took from the rear passenger door speaker for sound. For the last year though, my sub has had problems just shutting off during play, especially when I'd play several bass flexing songs, and I heard a theory that it could be the subwoofer going bad. Sometimes I can get it going again, if I hit the AC button, which makes me think that it's a power issue.

I have noticed too sometimes while I'm driving the seatbelt sign flashes on and off (which is weird no one else in the car but me and I have my seatbelt on), the lights and fan flicker worse, and a couple times last week the stereo shut itself off and then came back on again. So that makes me think that the battery is too weak to keep everything going. Probably getting worse. A couple days ago I went to get in my car and it wouldn't unlock my door and the ignition wouldn't turn over. I turned the fan off, and the AC, then finally I got it to turn over and the stereo wanted the 5 digit code to work.

I wonder about maybe installing a capacitor for the subwoofer maybe it won't take so much drain off the battery. I have the bass turned down so I hopefully don't have issues, but I'd like to be able to enjoy it again at some point. I wonder about installing a capacitor as well for the entire electrical system, since putting in a bigger battery doesn't seem like an option for the space.

if that's what could solve my problem at all.

any thoughts?

 

First of all ALL electrical power in the FIT comes from the alternator. The battery and if you install one, a capacitor are merely storage devices of power generated by the alternator. The battery and an capacitor will smooth out the short term voltage changes but that's it. So look at the alternator first. Monitor the output voltage and see if you have fluctuations in alternator output. You can get a cheap $15.00 voltage monitor and plugs in to your accessory / cigarette lighter outlet. If you see the fluctuations there then go back and run a wire to monitor the output of the alternator directly. If that looks good then start looking for intermittent connections especially the grounds. If the alternator appears to be the problem then remove it and have it tested and do not overlook the possibility of a slipping belt.

 

thx for the advice I'll check it out. I know power comes from the alternator but I mean that the battery just doesn't seem like a big enough one to hold the charge.. I think the alternator is working itself to death.

I now have a DRL light up on the dash, and driver's side DRL and hi beam doesn't work, although both low lights work fine. I researched it up to find one of three reasons: fuse, a small $25 grey box which holds resistance (causing fuses to blow), and a $300 relay box which could have gone bad. It's freaking raining like mad here today so no chance to get out there and mess with it.

 

Are you sure it's not simply a burnt-out headlight bulb? The high beams and the DRL use the same filament in the bulb, and the low beams are a separate filament. I'd check that long before verifying the other odds and ends of the DRL system. (Also, I suspect most of the components you've listed would affect both sides equally; I doubt there's a separate relay, resistor, or fuse for the driver's side and passenger's side lights. I may be wrong about that, though; I don't have a schematic diagram at hand.)