TommyN

The car is a Paul Neuman Chassis 57 Chevrolet Bel Air Convert. LS-1, 4l60, 3.55 gear. 1998 F-body engine , trans, and PCM. 110 volt early 90's chevrolet truck style alternator with a street and performance pulley set up and wiring harness. Have a 500 Ohm resistor in the feild side of the alternator. I have 2 gauge battery cable from ALT lug to starter and starter to battery. Ground on alt chassis and solid 2 gauge ground back to battery. Battery is grounded to chassis and engine and trans each have seprate groung straps. Field wire goes to key on. Sensing wire has been on the alt + lug and on a 10 gauge hot lead direct to the battery. Alt is running on a 1 3/4 pulley. Interstate mtp 24 battery with 800 CCA. Equiped with power windows, vintage A/C and basic sound system ( 2 small amps and navigation head unit ). The problem is the car will not charge more than about 10 volts at idle. Bring the idle up and charges @ 13 volts. Car is driven in city stop and go traffic and must be put into neutral and rpm's increased to charge. With lights, radio and heat blower there is a definite drain as evidence by the dim lights, as much as 2 volts. As I say during regular stop and go driving and quicker with accessories on the battery will not charge and loose charge to the point of almost not running. Any help or direction would be appreciated. Tom

Pop N Wood

iTrader: (1)

This is an excellent write up.

http://www.madelectrical.com/electri...esensing.shtml

You description of the sensing wire confuses me a bit. Should go from the alt sense connect to the main junction and/or something like the voltmeter under the dash. The alt + lug shouldn't have anything to do with the sensing wire?

FWIW the site I linked above use to say to not connect the sense wire to the battery or you risk overcharging the battery. Doesn't sound like your problem though.

I would also take the alternator to Autozone and get it checked.

Check out this page also. has a section titled "A couple of very important considerations " that warns
"There will never be a wire connected from the alternator directly to the battery."

http://www.madelectrical.com/electri...reewire3.shtml

TommyN

Alternator has been check by 2 shops. Battery in trunk. From Alternator the batt+ uses a 2 gauge to the starter + lug and 2 gauge back to battery. The 2 wires from the alt plug are the field wire or smaller wire to key on power with a 500 ohm resistor in line. The sensing or larger wire on the plug has been direct to battery + and also from the plug to the alt + lug. I seem to gain a volt from the lug hook up ( no voltage drop to back of car). Gauges are classic insruments which should be plug and go with an LS setup.

Shawn MacAnanny

iTrader: (12)

You need to run the same 12v to pin c i believe too since it's a truck alternater. Truck and vette alternators required power to two of the pins to get them to charge from everything i remember.

TommyN

It's not a LS truck alternator, it's a early 90's truck alternator. It charges just not at idle.

Carshopinc.com

iTrader: (5)

Does it just slowly drain down at idle with a load on it then? Are you brackets coated or anything, cause this could cause a case ground path problem.

TommyN

Alt case and all brackets are chrome plated. I know grounds on LS motors are important. I have a 2 gauge battery cable from the alt chassis to a engine ground. Engine and trans have a total of four grounds to the frame.

Pop N Wood

iTrader: (1)

Disconnect both of these wires and run a single wire from the alt sense plug to the back of your voltmeter or somewhere under the dash.

"There will never be a wire connected from the alternator directly to the battery."

Make sure your battery isn't going bad and sucking up too many amps.

Carshopinc.com

iTrader: (5)

it's not a wiring issue or a pulley ratio issue, the alternator is not capable of that kind of amperage and voltage..... I just ran into that with a vehicle that has alot of power options.... Powermaster makes a few really nice units that are rather pricey....

TommyN

Pop, got that in your first post, per the link I purchased a junction lug and installed. I did think the battery may be suspect so I swapped it out with one of my other know good batteries and same problem. I have not had time to drive the car since installing the junction lug.

TommyN

You feel the 110 amp alt is to small? This is the standard on a loaded early 90's suburban. I was told I can upgrade to a 140 amp. I am not sold on that just yet.

Carshopinc.com

iTrader: (5)

It's not that the unit is to small as per my application but at idle it does not have the capability to produce enough juice, off idle it's great..... I could increase the pulley ratio but then I would be afraid of it failing at high rpm. Right now it's 2400 alternator rpm at 800 engine rpm with a 3 to 1 ratio....