ls1 alternator problems.

[aziza z]

Just finished my swap just recently and while driving the car died and wouldnt start. I later found out my alternator wasnt charging. Thinking it was the alternator i switch it out for a new one. same thing happens. the car wont keep charge. i have one of those battery chargers/testers that tells if the alternator is charging and it says it isnt. It has only one wire that goes on top of the alternator (small red wire). after some reading i found out that this is the exciter wire that should have 12vs. it doesn't.

 

 

anyone know whats wrong here? any help is appreciated.

 

oh yea its an ls1 from a 2002 camaro ss.

[aziza z]

sent an email to speartech: this is the response.

 

Speartech wrote:

 

What you are reading is completely wrong. 12 volts on the red wire will destroy the regulator inside the alternator.

 

You would need to check continuity of the red wire from the alt. connector back to the PCM connector (PCM RED 15). If that is good the problem is either with the computer or other wiring on your car.

 

John

Speartech Fuel Injection Systems, Inc.

www.speartech.com

 

 

 

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thing is that when i have it pluged into the pcm like instructed the alternator doesn't hold its charge. what else could be wrong? i alt is brand new.

[VinhZXT]

Here is what comes out of my service manual:

 

"Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output #02-06-03-008A - (Jul 28, 2004)

Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output

1990-2005 Passenger Cars and Light Duty Trucks

 

2003-2005 HUMMER H2

 

This bulletin is being revised to add the 2004 and 2005 model years. Please discard Corporate Bulletin Number 02-06-03-008 (Section 06 -- Engine).

 

Any vehicle may have a low voltage display (if equipped with gauges), lights that dim at stop lights, slow cranking, no start, low generator output at idle or dim lights at idle when electrical loads are heavy at idle or under slow driving or infrequent usage conditions. These characteristics may be more noticeable with customer added electrical accessories, or with a discharged battery. These are normal operating characteristics of a vehicle electrical system and no repairs should be attempted unless a proven fault has been diagnosed.

 

During normal driving conditions, when engine speed is above 1000 RPM, the generator is designed to do two things:

 

Supply the current necessary to operate the vehicle's originally equipped electrical devices (loads).

Recharge/ maintain the battery's state of charge.

The following factors may affect generator and battery performance:

 

Non-usage of the vehicle for extended periods of time. The vehicle's computers, clocks and the like will cause the battery state of charge to drop (For example; 30 days in a parking lot and the vehicle may not start because of a dead battery or a vehicle which is driven only a short distance once a week may end up with a discharged battery to the point where the vehicle may not start). This would be considered abnormal usage of the vehicle and the normally expected result for the vehicle battery, generator and electrical systems.

At idle, vehicle electrical loads may exceed the low speed current (amperage) output of the generator and when this happens the shortfall comes from the battery. This will result in a drop in the electrical system voltage as the battery delivers the additional electrical current to meet the demand. This is equivalent to the brown outs experienced by homes and businesses when the electrical demand is more than the supply. See Figure 1.

Extended periods of engine idling, with high electrical loads, may result in a discharged battery. Attempting to recharge a battery by letting the engine run at idle may not be beneficial unless all electrical loads are turned "OFF".

Increased internal generator temperatures from extended idling can also contribute to lower electrical system voltage. As the generator's internal temperature rises, the generator's output capability is reduced due to increased electrical resistance.

The following are some typical examples of electrical loads:

 

System

Amperage Load

 

Rear Window defogger

25

 

Electric AIR Pump

25

 

Heated Seats

5 Amps per seat

 

Headlamps (high)

20

 

Blower Motor (High)

20

 

Headlamps (low)

15

 

Brake Lights

6

 

Windshield Wipers

6

 

Ignition

6

 

 

 

 

 

Depending on the vehicle application, generator current (amperage) output at engine idle speeds of 600-700 RPM can be as low as 35 percent of the full rated output. With enough electrical loads "ON", it is easy to exceed the generator current (amperage) output when the engine is at an idle of 600-700 RPM. This is a normal condition. The battery supplements for short periods of time. Items that affect the vehicle's electrical system current and voltage at idle are the number of electrical loads being used, including add-on accessories, and extended idle times. When the vehicle speed is above approximately 24 km/h (15 mph), the engine/generator RPM is high enough and the generator current (amperage ) output is sufficient to supply the current (amperage) requirements of the vehicle as originally equipped and recharge the battery.

 

Dimming lights at idle may be considered normal for two reasons:

 

As the engine/generator speed changes, so will the current (amperage) output of the generator. As a vehicle slows, engine/generator RPM slows, and the current (amperage) output of the generator may not be sufficient to supply the loads, the vehicle system voltage will drop and the lights will dim. Dimming of the lights is an indication that current is being pulled from the battery. If the battery is in a low state-of-charge (discharged condition), the driver will notice a more pronounced dimming than a vehicle with a fully charged battery.

When high current loads (blower, rear defogger, headlamps, cooling fan, heated seats, power seats, electric "AIR" pump, or power windows) are operating or cycled "ON", the generator's voltage regulator can delay the rise in output. This effect, usually at lower engine speeds, can take up to ten seconds to ramp up the generator output. This is done to avoid loading the engine severely. To increase current (amperage) output, additional torque is consumed by the generator. The engine computer (PCM) will ramp up engine/generator speed in small steps so engine speed variations are not noticeable to the driver. "

 

 

Good luck

[Bartman]

Not sure if your alternator works the same as mine, but I have the exciter wire hooked to the ground side of a charge light on my dashboard (don't use an LED). The positive side is hooked to ignition hot. When the ignition is turned on the light is on, and when it starts the light goes off. My alternator won't charge unless the exciter is hooked up to power, and using the light lets me know that the alternator is working.

 

Hope that helps.

[aziza z]

hey bartman

 

i hooked it up that way and the light never comes on but it has power going thru it.

[mobythevan]

I put a different rectifier in my LS1 alternator so it doesn't use the red wire from the PCM anymore. You can find the instructions and part number over on v8rx7forum.com

 

Works great.

[VinhZXT]

Let's double check a couple of things:

1. Continuity check on the small red wire back to the PCM like SpearTech mentioned.

2. Check the the connection between the big red cable from the alternator to the 12V battery.

 

If the above connections are correct it should work regardless of the light or not.

[aziza z]

well im an idiot. the big wire in the back was loose. thanks guys.

 

 

btw went for a drive today....my god, what a feeling. thing pulls like no other.