Hey all, today my brake and battery lights on my dash started flickering occasionally when my car went over bumps. By the end of the 20 minute drive, they are on and stay on, until a bump sometimes turns them off for in instant. Car drives fine, starts fine, acts fine otherwise. I just installed a new battery. The lights flicker in intensity over bumps, and pulling the E-Brake causes the lights to get brighter as if they were getting partial voltage.

Has anyone experienced similar issues? Search shows alternators cause this problem, but the connection to bumps and the fact the lights seem dim leads me to believe I've got an electrical fault somewhere else.

I may be paying for last weekend's bumpy autocross... LOL

 

You have the battery tie downs holding the battery so it's not flopping around? Trace the wires and check that all your connections are tight. Clean anywhere you see corrosion

 

Car idles with accessories and headlights on at 12.33 volts, lower than the 12.7 volts I get with the car off. That seems indicative of a charging issue to me. I'm going to check the alternator grounds visually. Should voltage at the alternator be battery voltage when parked? Anything else I can check before I throw an alternator at it?

 

What this guy said. I would not only check every ground but I'd remove each, hitting the painted area with some 80 grit (dremel) so that each ground is making contact with the panel, frame, etc. and it's not relying on the thread of the bolt and use dielectric grease in between each ground and it's respective panel. I did this while installing my diy stealth grounding kit as I've read these oem grounds can be problematic.

 

Poor installation, poor workmanship?


Check battery cables for tightness and lack of corrosion.
Check brake fluid

Telcoman

 

Problem solved:
I went through the ground system in the FSM, cleaned everything related to engine control or charging system, which seemed to fix the problem for 20 minutes until it stopped charging again on the test drive. I then confirmed the alternator wires show battery voltage when the problem is occurring, isolating issue to alternator after all. Easy but relatively time consuming (for a newb like me) DIY replacement using OReilly's Ultima rebuilt alternator w/ lifetime warranty, but make sure you have a Lilse-style spill free radiator funnel on hand or you're going to make a real mess bleeding the coolant which you need to drain to get the fan shroud off to get one of the alternator bolts off. Keep bleeding until heat burns your hand at idle. Also a good time to do belts/pulleys and radiator/heater hoses.

 

 

I have 2008 g35x. Approx 6 mos ago installed a rebuilt 150 alternator and right after new battery. I just changed out my plugs and noticed my brake light, battery light, key fob (sometimes) will come on if I idle for 5 -7 mins. I put meter on in morning 12.5 range, start it with air etc (load) on it will sho 14.4ish. If I idle in line or just sit idling, battery light comes on then brake etc. If i test it shows 11.5ish on and battery with meter. I go to autozone and they say charging and battery working fine. I stopped at o'reilys and they said fine. I let it idle and then it said battery weak voltage regulator issue? just went out after driving home 12.25??? Is it a Ground?? Everything was fine until I put new plugs in....Help...

 

If your engine is running and the battery voltage shows 11.5 your alternator isn't charging your battery. I get better voltage at the battery than that after sitting with the engine off and subs bumping for a half hour.

 

I'd start by opening up all the connection points that have been touched during the alternator and battery install. Use a wire brush and clean everything thoroughly, apply a light coat of electrical anti-oxidation grease DE-OX to all mating surfaces. Bolt everything back together and see if it fixes the issue.

Also do the grounding conductors while you're at it, both ends of the negative cable as well as the bonding jumper to the engine, it's located on the passenger side of the timing chain cover and bolts to the chassis directly below the coolant reservoir. Remove the single 10mm bolt from the coolant reservoir, lift it straight up (no need to drain coolant or disconnect the line). You will see the 2-hole lug bolted to the chassis.

 

I went through and checked grounds, took wire wheel and sanded grounds. We retraced backward the steps from changing the plugs and checked all connections. The original stock alternator was taken to an auto electric shop for possible rebuild. (50 yrs or so in business). The owner opened it up, said it looked fine, ran it for quite a while, and called saying the alternator is fine?????. We took the aftermarket cheaper alternator and put back the o.e.m. one. Everything seemed fine, I turned the ac on and 5 mins later the battery and brake lights were on and It went into limp mode half way home...Only thing is throttle relearn and clear ecm. Is it possible for a throttle body taken off and cleaned , never reset would cause a charging problem?? Help.... Thanks, Jm

 

brake + battery light = charging system problems. Might have missed this, but is your alternator charging your battery or not? Have you tried a new battery?

 

Could be the ground as well, check the engine bonding jumper, passenger side of the timing chain cover to the chassis directly below the coolant reservoir. Remove the single 10mm bolt holding down the coolant reservoir, lift it straight up with the hose still attached, no need to drain it there's enough slack.

Unbolt the jumper, clean the lugs, bolt, and mating surface with a metal brush, apply a light coat of electrical anti-oxidation grease, bolt it back together.

Then do the same thing to the battery terminals, negative wire is just another short jumper similar to the engine bonding one.

 

Hey bro, I have the same problem, I just installed a rebuilt alternator and a new battery. I have the brake and battery light on and the car will die when I shut it off. Where do I start off ?

 

Test the battery, test the alternator.