hey guys my lights on my 84 seem to be pullin alot of juice. what i mean is im running at 13.2v driving and about 13 to 13.1 with the lights on untill i run into a stoplight and as soon as i come to a stop boom my volts drop like 3rd period math. they go from about 13ish to about 12. and thats with nothing else on. if i give her a little gas at the light the volts jump up but fall real fast. the reason why i think its in my lights because is in the day time when i dont run my lights it hold strong at the stoplights. i put a 4ga wire from the alt to the batt. and that helped my charging but not when im ideling

any ideas
thanks for the help :cheers:

 

I would take it to autozone and have a meter put on it.Sounds like your alternator is going bad.It shouldn't have a low voltage drop no matter what lights are on.With the meter on it, they can put a load on and see what happens. :chevy

 

alt is about 4 weeks old. batt is good but hey its free ill try it tom. but i know what they are going to say

 

What is the lowest voltage you've seen?

 

well i never let it go below 12v if i see it drop below 12.2 or 12 i pop it in N and rev it a little, but i never just let it run down

 

Same thing on my 85. I will replace with a 140 next time. Have 120 on there now

 

I think your over reacting. My car does the same thing. I thought you were dropping into single digits. My car shows 14.4 at start up then drops, but never goes below 12.2. When I first noticed it, I was like you, and it was all I could look at.I think it's natural for it to fluxuate. :D

 

At idle speed and only the headlights as the additional load, the alternator should easily be able to maintain 14 v (cold), 13 v (hot). Parts houses don't normally check alternator performance at the alternator rpm with the engine idling, so they may check it and declare it ok (due to their higher rpm during the test). Check for an aftermarket alternator pulley that is larger in diameter than stock, this will cause your alternator to have limited output at idle. Is your engine idle speed normal or set low?


[Modified by jfb, 9:42 PM 2/3/2004]


[Modified by jfb, 9:44 PM 2/3/2004]

 

My car idles at 900 rpm. Go out to your car, start it up, turn on every bell and whistle ie: lights, fog lights, AC, stereo, and check the reading. Let me know what it says.

 

Belts can slip under load and not always make noise. Is it tight enough, not glazed? I don't know if an 84 is a V belt but if so, alternator pulley could be worn from slipping and even a good belt may not hold. If it's a serpentine belt, is your tensioner weak? An alternator pulls harder than any other belt driven accessory. Do you have black carbon where the cable end meets the battery? Check all your connections from the alternator to the battery, it's not unusual for older wiring or cables to have severe voltage drop from one end to the other. In other words, even if your alternator has good output, it may not all be getting to the battery. Always check output at the alternator and at the battery. Drop should be 1/2 a volt or less. Good luck.

 

Hey ther Cory00!

I saw that you put a 4g wire on the alternator, also check your ground(s). Alternator, battery and such, many times I've seen great size power wires but they often forget that the ground completes the circuit. Working in an audio shop I've see people run 4g power wires to amplifiers and use 12 or 16 g speaker wire for ground!!! Good luck! :)

 

I never thought of alt to battery cable being shot. how hard is that to replace? my 85 does the same voltage drop thing but it drops to 10.6...

 

it really sucks because every thing works and runs like a cham but the chraging system.


also this is my 3rd alt in about 6 months and when iget new alts. its the same reading


i have 8ga for my amp grounds





[Modified by Cory00, 3:06 PM 2/4/2004]

 

From the General (and your year wasn't any better):

Charging System - Low Voltage Display ON/Dim Lights

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 02-06-03-008

Date: August, 2002

INFORMATION

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

Models:
1990-2003 Passenger Cars and Light Duty Trucks
2003 HUMMER H2

This bulletin is being revised to update the model years and to update text. Please discard Corporate Bulletin Number 43-64-07A (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 to church only on Sunday 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.

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:

1. 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.

2. 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.

For diagnosis of the battery and or the generator, refer to the appropriate Service Information or Corporate Bulletin Number 02-06-03-006.