batt light slightly illuminating at low rpm...

[everpresentnoob]

So the last two days I have noticed that my batt light is barely coming on when my car is under 2k rpm. It isnt consistent, but it is happening. Im thinking my alternator is on the way out. The stock NA alt is an 80 amp while the TT alt is 90. Im thinking of dropping the 90 amp in. from what i read there are no fitment issues doing this, does any one disagree? are there anyother things I should check before dropping 150 on a new alt? I have put my meter on it and at idle I see over 13 volts, battery is about 2 months old.

[rgregoryb]

I took the cheap way out and bought one of those USB chargers that plug into the cigarette lighter and gives you a constant digital readout of the alternator output. I don't like the lights.

[everpresentnoob]

yea, I understand that. Im going to drop a wire from teh batt pos into the cabin and hook my Fluke up to it for my drive home. I just dont want to have a slowly dying alrernator that gives up its ghost half way through my 98 mile commute home.... If my alt is flaky I need to swap it. But if there is something else that could be causing that light to illuminate that is what i am wondering.

[rgregoryb]

I believe that you are on the right track. I don't know where you live but many auto parts stores can check the alternator. I also would go with the 90 amp.

[everpresentnoob]

Well, I ran some 16g wire from my batt into the cabin for my ride home and had the leads of my Fluke attached to them. on startup I had 14 volts, but within about 2 miles it was down at 12.35... the first 20 miles of my drive were through slow moving traffic 30 and under. Voltage stayed around 12.3-12.4 that whole time. occasionally I would see it dip to 12.19! when it did that if I was stopped and idling my batt light would slowly come on as well as the brake light beside it. when the brake like came on it wasnt steady but kinda visually buzzing and there was something under the dash that was buzzing with it. Not loud, but I could definately tell something was going on. Finally got out of traffic and once I hit 5th gear the voltage jumped to 14.2. Well for a few miles at least. then it would slowly drop back down to 12.4 and stayed there the remainder of my drive.

When I got to my town I went to the local Auto parts store and had them check it. their machine said my alternator was not putting out anything. yay. Ordered a new alternator adn it shold be here tomorrow.

But Im wondering how the hell I made it home if the alt was dead? 98 mile drive people!!

Got home and puled the battery out of the Z and put it in my SE-R. Guess the Z is parked untill I get a chance to pull he alternator nad replace it. Lets see, the next day I have off is.. around april 20th... We got a number of things going on at work and I am the only one who can cover a lot of them. Any one near DC area wanna change my alt for me?

[rgregoryb]

I am just amazed that you travel 98 miles each way in a Z.I am near Birmingham just drop it by.

[everpresentnoob]

well its a fun car to drive... Yea, if it drives 98 miles with an apparently dead alternator Im sure itll make it 738 to you...

[everpresentnoob]

well, figured I would update this. Dropped a new 90amp alternator in it and wired a small digital voltmeter to the battery. 90 mile drive this morning in 20 degree weather and my voltage sat at a nice steady 14.3. When coming to a stop in traffic it would drop to 13.8 and then slowly climb back up to 14.1. Guess my issue is solved. I was worried it was gonna be that harness i keep reading about from the alt to the trans.