1999 Chevrolet Blazer battery draining

Tiny
PSHARKDIZZLE
  • MEMBER
  • 1999 CHEVROLET BLAZER
My car sometimes doesnt start, but if I charge it overnight it works great, and continues to for a couple days. If I dont run it everyday, a few days down the road it rarely starts. Sometimes when im driving the battery light will come on and the car stops. Usually it does start right back up, but it does happen every once in a while. I did get the battery tested and it tested fine. I have looked to see if any lights remain on when im away from it but thats not the case
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Monday, October 5th, 2015 AT 4:51 PM

4 Replies

Tiny
CJ MEDEVAC
  • EXPERT
ALL RIGHTY THEN

GOOD DEAL WITH THE BATTERY TESTING ('COURSE IT WILL BE LOW AGAIN IF IT'S GETTING DRAINED.)

LET'S DO POWER SYSTEM 101 STUFF 1ST

PLEASE SEE MY ANSWERS AND PICS IN MY LINK BELOW

http://www.2carpros.com/questions/1996-chevrolet-tahoe-wont-start-sounds-dead-battery-jumpbox-get-same-reults

LET'S SAY YOU REALLY DUG DEEP ON THAT LAST ONE, AND STILL NO DICE

LET'S DIG IN THE TOOL BOX OR GO TO "HARBOR FREIGHT" FOR A DECENT $5 DIGITAL VOLTMETER.

JUMP OVER ON "YOU TUBE" SEARCH FOR AND WATCH SEVERAL VIDEOS ON "PARASITIC DRAINS", LET'S GO WITH THE MOST PROFESSIONAL SOUNDING ONE IN THERE.

DO YOUR THING!

IF YOU ARE ABLE TO UNDERSTAND MY S.C. HILLBILLY WRITING HERE IS AN EXAMPLE OF A PARASITIC DRAIN MY BUDDY HAD, IT'S NOT ALWAYS A LIGHT LEFT ON!

http://www.2carpros.com/questions/2005-kia-sedona-car-keeps-losing-battery-power

NOW THAT YOU HAVE A VOLTMETER YOU CAN DO VOLTAGE TESTS ON YOUR CHARGING SYSTEM. THIS IS NOT AN "ALL OUT/ FULL SCALE TEST" (AS AT A PARTS STORE) BUT IT WILL LET YOU KNOW IF WE ARE GETTING JUICE TO THE BATTERY FROM THE ALTERNATOR.

ALTHOUGH BOTH THE BATTERY AND ALTERNATOR MAY BE A-OK, IF THERE IS A "BREAK" OF SOME SORT BETWEEN 'EM, THE MISSION CANNOT BE ACCOMPLISHED

SO QUICK TESTING

SET THE VOLTMETER ON 20 VOLTS DC (OR THE NEXT VALUE HIGHER THAN 12 VOLTS, IF THERE IS NO "20")

TEST 1) VEHICLE OFF- BLACK LEAD ON NEGATIVE, RED ON POSITIVE BATTERY POSTS- A GOOD BATTERY WILL BE 12.5 VOLTS OR SO

TEST 2) CRANK HIM UP!

PERFORM THE EXACT SAME TEST ON THE BATTERY

IF WE ARE GETTING ALTERNATOR JUICE TO THE BATTERY, THE VOLTAGE WILL NOW BE AT LEAST 13.8 VOLTS MAYBE EVEN UP NEAR 14.5

IF THERE WAS NO CHANGE IN TEST 1 AND TEST 2, WE NEED TO TRACE DOWN WHY THE ALTERNATOR IS NOT FEEDING THE BATTERY

CAN YOU HANDLE ALL OF THE ABOVE?

YOUR TURN

THE MEDIC

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Monday, October 5th, 2015 AT 7:40 PM
Tiny
CARADIODOC
  • EXPERT
Hi brother CJ. I know they'd rather I didn't do this, but I feel compelled to add another chapter because I suspect there's something else going on here. The "Battery" light can turn on for a few different reasons other than a no-charge condition. If this were a true no-charge problem, the battery would run dead after less than an hour of driving, and much faster on GMs with their daytime running lights that turn themselves on. The fact the battery holds up for a few days is typical of an under-charge due to a failed diode.

With one failed diode of the six, you will lose exactly two thirds of the generator's output current capacity. Psharkdizzle didn't bother to list the engine size or transmission type so I can't look up what is normally in there, but for the common 90 amp generator, 30 amps is not nearly enough to meet the demands of the entire electrical system under all conditions. The electric fuel pump, head lights, ignition system, and radio alone can draw over 25 amps. That 30 amps you might be able to get is only at a higher engine speed. At idle you'll be lucky to get 10 amps. Use the brake lights and power windows a few times, or use the heater fan, and there's no way a generator with a bad diode can keep up. The battery has to make up the difference until it slowly runs down over days or weeks.

The misleading part of this is the charging voltage as measured at the battery with the engine running, as you correctly recommended, will usually appear to be just fine, within that acceptable range of 13.75 to 14.75 volts, (a little more or less depending on which text book you look at). What that voltage test is good for is to see if you have something or nothing, but the second part of the test requires a professional load tester. If battery voltage stays at 12.6 volts or less with the engine running, there is no current coming from the generator at all. If the voltage is in the acceptable range, we only know there is some output from the generator. That's when the load tester is needed. That will test for full-load output current and "ripple" voltage. If one of the diodes has failed, ripple voltage will be high, and, as I mentioned previously, the maximum current will be exactly one third of what it's supposed to be.

Psharkdizzle, there's no way to suger-coat this. In my opinion, GM had the world's second best generator design through the 1986 model year, but for 1987 they redesigned it, and it's one of the worst designs ever. Due to their design, they develop huge, harmful voltage spikes that can damage those internal diodes and voltage regulator, and interfere with computer sensor signals. This is where the test you had done on your battery is invalid for this symptom. The battery is the key component in damping and absorbing those voltage spikes, but as they age and the lead flakes off the plates, they lose their ability to do that. They will still crank the engine just fine so they'll work in an '86 or older car. It is real common to go through four to six replacement generators in the life of a GM car, but to reduce that number of repeat failures, replace the battery at the same time, unless it's less than about two years old, even if it's cranking the engine normally. If you do not replace it, expect the replacement generator to fail again anywhere from five minutes to five months. This is such a common problem, I copy and paste a standard reply rather than retyping it every day. People post your same symptom here over and over.

Also, to clear up any potential misunderstanding, the "Battery" light really has nothing to do with the battery, at least not directly. That light should say "Charging System". It means the generator is not recharging the battery as you're driving. As I mentioned, with a dead charging system, a good, fully-charged battery will have a hard time running the electrical system for a full hour. Since yours lasts much longer than that before you have to charge it again, you can extend your driving time by turning off everything electrical you don't need. Have that professional load test performed, then let us know what was found for full-load current.
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Monday, October 5th, 2015 AT 9:14 PM
Tiny
PSHARKDIZZLE
  • MEMBER
Hello,
sorry I didnt mention it before, its a 4.3L V6 engine. I really know next to nothing about vehicles, but I did try the parasitic load test, and it seemed nothing was wrong. I dove a little deeper searching for answers and some people said I need a new "ignition switch"? Does that sound like it could solve my problem? I charged the battery a week ago, it still started up, but took longer and longer as each day went by.

Thanks,
Patrick
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Saturday, October 10th, 2015 AT 7:23 AM
Tiny
CJ MEDEVAC
  • EXPERT
PRETTY MUCH THE OTHER FELLER (CARADIODOC) ("DOC"), FROM WHOM I SORTA TAKE AFTER WITH THE LONG WINDED ANSWERS! LOL!

HE IS WELCOME TO ADD TO/ COMMENT/ SCOLD ME ON ANY POST I HAVE ANSWERED, "DOC" IS A TEACHER, HE USED TO TEACH AUTO MECHANICS (I THINK HE'S RETIRED NOW)

HE SUGGESTED IN THAT LAST LONG ANSWER THAT THE ALTERNATOR DIODES COULD BE THE PROBLEM. SNATCHING IT OFF AND HAVING A FULL ALTERNATOR TEST PERFORMED MIGHT SAVE YOU FROM ANY FURTHER SEARCHING

EVEN DISCONNECTING IT COMPLETELY SHOULD DROP YOUR "DRAW" WHILE PERFORMING A PARASITIC DRAW TEST

I WOULD BELIEVE THE IGNITION SWITCH WOULD EXHIBIT THE SAME SYMPTOMS EACH DAY.

WE'LL LET DOC THROW IN HIS VIEWS AGAIN!

IN THE MEAN TIME, THINK ABOUT HOW WONDERFUL IT WOULD BE RIGHT NOW IF YOU HAD A JEEP CJ! LOL!

THE MEDIC
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Saturday, October 10th, 2015 AT 7:48 AM

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