What's up guys I've noticed with the key on the ON position, my voltmeter shows 12.4-12.5. Once I turn on the car the volts clock in at 13.9-14.0 and within about 20-30 minutes of driving they go down steadily to around 13.2-13.4. This is with no additional load aside from my boost gauge, PLX wideband, an Apexi AFC and the voltmeter itself driving around during the day.

At night though with the headlights on and the car idling the volts come in at 12.5-12.8 or 13.0 at best and if I switch the oem foglights on it goes down to anywhere between 12.0-12.2 sometimes lower. With either or on (headlights & foglights), or both, the idle is very rough and sometimes the car shuts off when coming to a stop.

I'm running a 130amp Alternator with a 4 gauge wire going straight to the battery. I was running an Odyssey PC680 battery but have since switched back to a conventional Autostart Gold battery from Advance Auto to see if it was the battery but with no luck, same issue. I've also upgraded the big "3" to 4 gauge wires as well.

I was told that this may be an issue that could be solved by upping the idle but turning the idle screw on the throttle body hasn't helped either. It idles around 800-840 right now so I was thinking about maybe bringing it up some thru Crome to see if that changes anything but any other ideas out there?

Just in case its a 92 civic with a boosted LS running 1000cc injectors again using Crome, no AC, no PS and running a Fluidamper crank pulley. Any help would be greatly appreciated.

 

Is the crank pulley or alt pulley an underdrive pulley ? If not you need to see how many amps your alternator is putting out once it gets hot.

 

Alternator pulley is stock and crank pulley is Fluidamper, smaller than OEM. How could I go about measuring the amps? Could I pull it and bring it into say an Autozone to check that?

 

Nah that won't tell you anything, you need to measure it on the car. Any place that will check it off the car checks them at 2k rpm or so . I am guessing it is not spinning fast enough at idle. Normally if you have an alternator only shop in your town they may check it for free or very little charge. they would be the ones to suggest a fix like smaller alt pulley. I take it that if you hold the rpm at 1000 or more the voltage is correct ?

 

I have to agree, find a batt./alt. shop, [Interstate batteries] and have them do a proper load and gravity test, most shops will do this for free, it only takes a few minutes. 94

 

RHD - Your right, I never have any problems above 1000 RPMs or when I'm driving, only when I come to a stop & on idle with the lights/foglights on.

It's funny you mention the pulley because I remember reading an article someone posted during their install and they mentioned their high output alternator having a smaller pulley but the one on my 130 amp is the same size as the OEM pulley.

FCM - So you say Interstate would be able to do this? Sh*t there's one a block away from my house; I thought they only dealt with batteries, I'm going to have to check them out. Hopefully sometime this week if not the weekend.

I just dropped $100 on this 130 amp alternator so I hope I dont have to cop another one...

 

As far as I know, all Interstate batt. distributors must have a test unit, we do, and so does the main distributor and all the other distributors in this area and as Interstate batt. are warrantied at any Interstate distributor, it makes sense they all have the test equipment.

 

Stock pully on the Alt and a small pully on the Crank will result in lower RPM of the Alt...try undersizing the alt pully that may speed it up enough to compensate...Volts drop off a bit as temp rises due to resisteane on everything going up as it heats up. Its not an Alt or battery issue if its all ok above idle. Your Alt will bench test fine you need to check it on the car under the conditions you have a low voltage at.