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Battery Light ON
03-31-2010, 06:20 PM
#1
1st Gear Member
Thread Starter
Join Date: Feb 2008
Location: Seattle Washington
Posts: 79
Battery Light ON
So very intermittenly about a month or so ago my battery light would flicker on just for a breif moment and go back off. It came to the point that it would stay on longer and longer at random periods of time and more often (highway, city, cold, hot, cruising, light load, heavy load) it really had no rhym or reason to it as to when itd come on. So i went down and had an idiot kid do a check on my alternator and batter load test and they both look good according to the monkey pushing buttons. So i check alternator and battery connections look for corrosion and again i find nothing. (I live in wa no salt here :P) Anyway ive heard this may possibly be a (high voltage) condition as well or overcharging of the battery? Ive expierience absolutly no starting problems or other issues other than the light going on and off. Could it be the belt slipping on alternator pully? No cracks has decent tension but ive never replaced 55k miles. I also have been keeping close eye on the voltage gauge and its steady where its always been. I have seen a few posts here and there but couldnt find many on this site thought id see if anyone had some suggestions getting PISSED >( Definatly not ina position to pay someone to fix i just got my second speeding ticket anyway thanks for any input.
03-31-2010, 09:54 PM
#2
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
The "battery light" is directly controlled by the voltage regulator, which is in the generator. Here's the system overview from the shop manual:
Here's the description of how it works:
I would check both fuses (F1.20, 20A in the BJB; and F2.5, 15A in the CJB) to make sure they are seated properly and not intermittent. Check the wiring of course, and then if the problem persists replace the generator.
Here's the description of how it works:
The generator is belt-driven by the engine accessory drive system.
With the ignition key in the run position, voltage is applied through the warning indicator I circuit to the voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit to the generator field coil.
When the engine is started, the generator begins to generate alternating current (AC) which is converted to direct current (DC) internally. This current is then supplied to the vehicle's electrical system through the output terminal (B+) of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the internal regulator. This voltage feedback signal (typically half the battery voltage) is used to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the A circuit. This A circuit voltage (battery sense circuit) is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain the correct generator output.
The set voltage will vary with temperature and is typically higher in cold temperatures than in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.
With the ignition key in the run position, voltage is applied through the warning indicator I circuit to the voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit to the generator field coil.
When the engine is started, the generator begins to generate alternating current (AC) which is converted to direct current (DC) internally. This current is then supplied to the vehicle's electrical system through the output terminal (B+) of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the internal regulator. This voltage feedback signal (typically half the battery voltage) is used to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the A circuit. This A circuit voltage (battery sense circuit) is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain the correct generator output.
The set voltage will vary with temperature and is typically higher in cold temperatures than in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.
03-31-2010, 10:10 PM
#3
Retired Moderator
Join Date: Jun 2006
Location: SF Bay Area
Posts: 9,235
Pepe the Cliffster goin all tech on us... right on 
I would add that one can get a voltage meter and have your buddy run the RPM's up to 3K or so and read the voltage at the battery terminals. Confirm you have over 14 volts at this engine speed.
Jazzer approves the above post
I would add that one can get a voltage meter and have your buddy run the RPM's up to 3K or so and read the voltage at the battery terminals. Confirm you have over 14 volts at this engine speed.
Jazzer approves the above post
03-31-2010, 10:52 PM
#4
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
If you want to test this stuff on your own just get a multimeter and one of these--100A HF battery tester, or better yet this puppy; 500A HF battery tester.
The 100A unit is often on sale for $20, I got the 500A tester a few years back for $30. The 500A unit is badass as you can dial up the load as things are running and see where it hits the fan...
04-02-2010, 02:34 AM
#5
1st Gear Member
Thread Starter
Join Date: Feb 2008
Location: Seattle Washington
Posts: 79
haha nice ill get right on that friday on my day off! i got some vets responding to my posts nice! thanks for the good info guys ive read a **** ton of your guy's posts i shall try to be more active in our forum rather than being an info mooch and share the wealth. Ive been kinda pullin my hair out over this im excited to start breakin it down and fix it muchos gracias.
04-03-2010, 01:42 AM
#6
Join Date: Mar 2008
Posts: 14
Easy one. Mine did the same thing.
Get your battery checked, if it is good...then your alternator is dying. At first I had a guy put in a new voltage regulator for about half the price of a new alernator...but even that after that new part, the light went out..but the alternator still died in about 2 weeks (all of a sudden like). Got new alternator from autozone, lifetime waranty. Have not had a problem since.
Get your battery checked, if it is good...then your alternator is dying. At first I had a guy put in a new voltage regulator for about half the price of a new alernator...but even that after that new part, the light went out..but the alternator still died in about 2 weeks (all of a sudden like). Got new alternator from autozone, lifetime waranty. Have not had a problem since.
07-08-2010, 02:20 AM
#7
1st Gear Member
Thread Starter
Join Date: Feb 2008
Location: Seattle Washington
Posts: 79
Car still runs great fuses are seated spot and wiggle checkd the wiring harness's battery has good voltage alternator is reading 14 and some change.... I guess ill just roll with it for now and see what happens
07-11-2010, 01:16 PM
#8
Join Date: Jul 2010
Location: Arizona
Posts: 23
Mine does the same thing! It started 3 weeks ago. I have a Diablo Predator and have run logs while driving. I've also had the battery / alternator tested. The battery was reported as "bad" and looked original so I purchased a new one. Five days later, the same intermittent light. While driving and logging voltage with the predator, I'm gettin 14.1 volts or so. The voltage does drop down on my commute, 45 minutes, down to 12.8 towards the end of the ride. I'm assuming the battery is pretty much charged at this point. My guess is that the alternator is having problems, just not enough to see with the logging on the predator.
If you're replaced your alternator, report back and let us know if that's the problem. I'm going to hold out on the alternator until I decide if I'm doing underdrive pulley's or not.
If you're replaced your alternator, report back and let us know if that's the problem. I'm going to hold out on the alternator until I decide if I'm doing underdrive pulley's or not.
10-02-2011, 05:59 PM
#9
Join Date: Oct 2011
Posts: 1
Hi folks, new to the forum.
I'm having a similar problem - intermittent battery light. I just put in a new (remanufactured) alternator, and I get good charging voltage at the battery. Even with lights, fans, turn signals and wipers on, I get 14 volts at idle.
Before I replaced the alternator, what would happen is that having everything running would result in battery discharge, and the lights would dim at low RPMs (and the battery voltage meter on the dash would start dropping). I'd have to put it in park at intersections and hold down the gas to keep the RPMs up. All that time, I never saw a battery light.
From earlier posts in this thread, I gleaned that the alternator directly controls that light. Is the new alternator faulty in some way? Other than the intermittent light, it seems to be working properly (but we'll see how it does in stop-and-go rush hour traffic tomorrow). Would I be justified in taking it back to Autozone to swap it for another one?
I'm having a similar problem - intermittent battery light. I just put in a new (remanufactured) alternator, and I get good charging voltage at the battery. Even with lights, fans, turn signals and wipers on, I get 14 volts at idle.
Before I replaced the alternator, what would happen is that having everything running would result in battery discharge, and the lights would dim at low RPMs (and the battery voltage meter on the dash would start dropping). I'd have to put it in park at intersections and hold down the gas to keep the RPMs up. All that time, I never saw a battery light.
From earlier posts in this thread, I gleaned that the alternator directly controls that light. Is the new alternator faulty in some way? Other than the intermittent light, it seems to be working properly (but we'll see how it does in stop-and-go rush hour traffic tomorrow). Would I be justified in taking it back to Autozone to swap it for another one?
10-02-2011, 08:52 PM
#10
2nd Gear Member
Join Date: Mar 2011
Location: California
Posts: 170
I had same problem and it was my alternator. I replaced it with a oem dealer alternator and the battery light remained on! It turned out the oem alternator was defective, so I took it back, got a new one again and its been fine since. I've also had many autozone products come defective, so I would take it back, get another one and then go from there.