Battery light turns on under WOT/Full boost?

[jstrebel]

Any reason why the battery light would come on under WOT and full boost? When I let off the gas it turns off.. then comes on again at full boost.

recent changes:

1. Replumbed the intercooler piping to fix a known leak.
2. Added NGK R5672A-8 race plugs gapped at .30. These plugs are equivalent to bkr6e's. I went 2 steps colder for 2 reasons. A the summer is coming and the car pings like a mo-fo all summer, and 2 I have a track event this saturday.. 85 degreess and WOT for extended periods at the racetrack.. = high heat.

I cleared 3 codes related to the leaking intercooler piping... no codes are coming up.

[ScaryGary]

Had a buddy with an accord that tripped the battery light at higher revs, and when he got the engine hot driving hard. It was directly related to a failing alternator.

[OverSpun]

^^ thats what I'd guess too.

[johnouellette]

e46 m3's are none for doing the same thing when the alt starts to die. That would be the first thing I would try changing, especially if you're going to track the car.

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Bump from the dead... anyone else have any ideas?

[imnuts]

Bump from the dead... anyone else have any ideas?

My GF has an E46 3-series that had the battery light coming on when accelerating (not just WOT), and a few days later the car wouldn't start. Alternator was replaced, car jumped and it's been working fine since then.

[jstrebel]

yah, the culprit was a failing alternator..

[bwoy1981]

Happened to me like 2 mths ago when my alternator was dieing. I had to get it rebuilt.

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I'm thinking my car is cursed.

I am on part throttle and spool up to 16psi the light goes on, I lift off the throttle and it goes away. Go WOT and the light comes on, lift and it goes away.

So it's the alternator?

Well that would also explain the coilpack issues I have been having too.

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Boys at the shop told me to go log block 004 and turn the battery light doing a WOT rip and see what the log says.

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My car is cursed.

Took it out the last couple of days to log block 004 when the battery light goes on during WOT and guess what happens?? No light.

Logged 004 anyway and compared it to my g/f B7 and it is at times 0.4V lower than her readings so I don't think the alternator is dying.

[bwoy1981]

Hmmmm check the ground on your alternator ... make sure the wire isn't broken or touching anything.

[B6Lovin]

mine does this. it actually misfires some when you get into really high boost (25+)
oh, and my ipod thingy will shut off/the radio cuts out sometimes when i really flog it

just no monies for a new alternator.

lol

[bwoy1981]

damn.. well if u have to get it rebuilt. I paid $160 and its pushing more amps than a factory unit. Autozone wanted like $300 and the dealership wanted like $885

[BerNur]

whats the update man im getting this same issue now as well its scary seeing any red lights period...

[A4SoftWalker]

Mine is bass ackwards - full throttle and the headlights turn out and come back on.

Loose my cruise ctrl setting.

Whole car goes wacked for a second. At night people think I'm flashing them....


And NO BAT LIGHT....

[rbj325]

Mine is bass ackwards - full throttle and the headlights turn out and come back on.

Loose my cruise ctrl setting.

Whole car goes wacked for a second. At night people think I'm flashing them....


And NO BAT LIGHT....

I bet your blinkers and windshield wipers don't work either when this happens.

[hcaudikeed]

That's the voltage regulator in the alternator going bad. You'll need a new alternator. Same thing happened to me on a newer rebuilt alternator.

[A4SoftWalker]

I bet your blinkers and windshield wipers don't work either when this happens.

How'd you guess ... Well seems like alternator @ 116k I'll do some voltage logging 1st to confirm

[heateris]

damn.. well if u have to get it rebuilt. I paid $160 and its pushing more amps than a factory unit. Autozone wanted like $300 and the dealership wanted like $885

Were did you get it rebuilt?

[rbj325]

How'd you guess ... Well seems like alternator @ 116k I'll do some voltage logging 1st to confirm

I'm dealing with this right now. It's such a HUGE pain to not be able to accelerate and use your blinkers... it makes me feel like an ass hole. Plus accelerating in heavy rain is just suicidal when your wipers stop working.