Help: Battery, Alternator, or Connection Issue?
 

I've been having bit of a puzzling issue with my G35 coupe (2005, 6mt).

This started Monday after I pulled over to gas up. When I got back into my car to start it all lights came on as usual but when I turned the key to actually start the engine all that happened was it clicked once than all electrical power was lost.

A few minutes later a couple lights would come back in (but very dim) and the key remote can unlock/lock the car. I got a jump from someone and the car started up right away. I drove home (Vancouver - Coquitlam) fine.

The next morning, the same issue happened again. Turn key to start, click sound, all electric power lost. Jumping the car again started it immediately. After I got to work, I turned off my car and then started it again with no problems.

Leaving work yesterday I had no problems starting and made it home fine. When I got home I turned the car off but the issue happened again when I tried starting it.

I required another jump start today morning, but this afternoon the car started up perfectly fine after being parked for a few hours at work (I tried about 4-5 times in a row: start, run for a minute, turn off).

The battery is still fairly new (installed September last year) and there are no aftermarket stereo accessories.

A similar issue was happening last year but stopped until this week when the new battery was installed.

Anyone have any idea on what could be causing it?

Edit: Had no issues yesterday after getting a jump in the morning. Started up fine after work and when I got home. I installed a new battery just in case and will wait and see if the issue persists.

Sound like your Alternator won't charge.

If it's an alternator problem, I should have the electronics dying when I drive though right?

I'll try to get my hands on a voltmeter and check tonight though.

check with a voltmeter you should see your voltage sitting between 14.5-15.5 approx. a dead cell on a battery can also cause the same concern.

very easy way to test alt vs battery.. start the car.. now take the negative off a battery.. if the car dies, its the alternator. if the car runs its the battery

a voltmeter would be best to test if there is a connection issue somewhere

Seems like a bad connection somewhere.

Have you checked the wires and clamps going to the battery?

Double check that your battery terminals are properly tight and clamping the posts. I had an issue once where the post was a touch too small, so when things heated up the clamp expanded and didn't make good contact.

I second the bad connection at the terminals diagnosis.

definitely check for lose/bad connections first leading to the battery and then proceed to alternator & battery test.

Incorrect - everything will continue running off the battery.

Eventually, the lights will dim and engine will run like shit, then die.

I say it's a connection problem cause it's intermittent and fires up with a boost (more amperage to overcome a bad connection).

If the alt was bad, it would eventually drain the batt and when he went to boost it, it would start but as soon as you disconnect the cables, the engine would die.

If the batt was bad, it wouldn't start sometimes - it would only start with a jump every time.

True, but it won't all just die instantly. Lights will probably be a bit dimmer since they're only running at 12V instead of ~14.5, but other than that, the thing would keep running for a while.

+1

Without a load tester it's really hard to say. Right now we are all just guessing.

Sure, but most are reasonably educated guesses based on experience and the described symptoms.

Depends on the car, with no alt my car will limp along at best, any attempt to go above a fraction of throttle and it bogs.

Survey says..........????????

This is also a very easy way to potentially damage the electronics in your car.

I think you should ask the repair shop, Battery, Alternator, or Connection

If your alternator was pooched you wouldnt be able to drive from Van to Coq on a dead battery. So Id be inclined to think battery or connection. DO NOT ATTEMPT TO RUN YOUR ENGINE AND DISCONNECT YOUR BATTERY TO SEE IF THE ALTERNATOR IS FINE. That will fuck up a good alternator in a hurry leading you to think you need an alternator when you more often then not didnt.