Mechanics

WHY ARE MY LIGHTS FLICKERING AND MY CAR LOSING POWER?

2007 Jeep Liberty • 70,000 miles

2007 jeep liberty with 70K miles. Car would not start this morning, I jumped it and it started immediately however the lights flicker during driving and the car seems to hesitate. I drove it for roughly 20 mins and tried to start it again and got no response. Is this battery or alternator?
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Davidsimkins
May 20, 2012.




Yes.

Measure the battery voltage before starting the engine and after. Holler back with those numbers.
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Caradiodoc
May 20, 2012.
I am stuck on duty and I dont have a volt meter. The battery is the original so it is probably time to swap it. I just dont understand why the car was hesitating and the lights would flicker while driving.


Tiny
Davidsimkins
May 20, 2012.
Alternators produce ripple which is a slightly pulsing voltage that is smoothed out by the battery. As the battery ages, it loses its ability to do that effectively, but to have noticeably flickering lights there is usually something else going on.

The first thing is to measure the battery voltage. It must be close to 12.6 volts. If it is closer to 12.0 volts, it is good but discharged. If it is around 11.0 volts or less, it has a shorted cell and must be replaced.

Next, with the engine running, battery voltage must be between 13.75 and 14.75 volts. If it is low, measure the voltages on the two small wires on the back of the alternator. One will have full battery voltage. The other one will tell what the system is doing.

If the charging voltage is okay, a professional load test will determine if the alternator has a bad diode. That will cause real high ripple and flickering lights. Computers are very intolerant of fluctuating voltage and will cause all kinds of symptoms including engine hesitation. An alternator with one bad diode will lose two thirds of its capacity, so a common 90 amp unit will only be able to supply 30 amps. That's barely enough to run the electric fuel pump, ignition and fuel injection systems, computers, and a few lights with nothing left over to recharge the battery.

If you care to know more about ripple and the problems it causes, check out the last section on this page:

http://randysrepairshop.net/charging-systems.html


Caradiodoc
May 20, 2012.
So, in other words, I would probably be better off replacing both the battery and the alternator.


Tiny
Davidsimkins
May 20, 2012.
THE BATTERY MAY NOT BE THE PROBLEM (OR IT COULD BE), IT COULD BE THE ALTERNATOR IS NOT CHARGING THE BATTERY....AGAIN, THE ALTERNATOR MAY NOT BE BAD.....BUT THE WIRING "PATH" BACK TO THE BATTERY MAY HAVE A BREAK IN IT....LIKE A BLOWN FUSIBLE LINK

YOU ARE NOT GONNA KNOW FOR SURE WHAT TO EXAMINE/ REPAIR UNTIL YOU HAVE MORE INFO

YOU NEED TO GET THE BATTERY AND THE CHARGING SYSTEM TESTED, WHAT BETTER PLACE THAN A POPULAR AUTO PARTS STORE?....THEY WILL USUALLY DO THIS FOR FREE

IF YOU ARE IN A BIND........

AS FAR AS GETTING THERE, DAYLIGHT HOURS WOULD BE BEST (STORE MORE LIKELY TO BE OPEN TOO)

IF THE STORE AIN'T TOO FAR OUT, GET YOUR VEHICLE RUNNING, IF YOU HAVE ELECTRIC WINDOWS ROLL 'EM DOWN....TURN "OFF" EVERY LUXURY ITEM YOU HAVE

NEXT--WHILE YOURS IS RUNNING, HAVE YOUR PAL "JUMPER ONTO" YOUR BATTERY AND "CHARGE YOUR BATTERY" WITH HIS RUNNING VEHICLE (THIS IS, PROVIDED THAT YOUR BATTERY WILL ACCEPT A CHARGE. 20 TO 30 MINUTES MAY "GET YOU BY" FOR A WHILE.

YOUR BATTERY MAY HAVE TO RUN THE FUEL SYSTEM AND IGNITION SYSTEM ALL BY ITSELF. YOU GOTTA CONSERVE THE BATTERY POWER.....SO, INSURE ALL UNNECESSARY STUFF IS TURNED OFF (LIKE LIGHTS, A/C, ETC)

HAVE YOUR BUDDY FOLLOW ALONG TO ASSIST YOU IF NEEDED, WHEN YOU HEAD OUT

IF YOU ARE NOT IN A BIND,

SNATCH YOUR BATTERY AND TAKE DOWN TO HAVE IT TESTED---IF IT SHOWS GOOD, RE-CHARGE/ RE-INSTALL, INVESTIGATE THE ALTERNATOR AT THE PARTS STORE

JUST A QUICK TEST "YOU" CAN DO IS TO SEE IF THE ALTERNATOR IS CHARGING OR WHAT THE VOLTAGE IS THAT IS ACTUALLY PRESENT IN YOUR BATTERY, AND THE CHARGE DOES GET BACK TO THE BATTERY.....YOU WILL NEED A VOLTMETER, SEE THIS LINK.....ACTUAL BATTERY CONDITION, NEEDS A BETTER TESTER (LIKE AT THE AUTO PARTS STORE)

http://www.youtube.com/watch?v=Bzz7P3qNHcE

KEEP US POSTED

THE MEDIC



Tiny
CJ MEDEVAC
May 20, 2012.
If the battery is the original one, it can be expected to fail soon. Five years is about as long as they will last, so you can replace it now, but don't replace the alternator unless testing shows it has a problem. That's money wasted if a new one isn't needed and it's not unheard of for a rebuilt one to have a problem that got overlooked.

If testing shows the alternator is not charging at all, measuring the voltages on the two small wires on the back of it will tell us where to go next in the diagnostic procedure.


Caradiodoc
May 20, 2012.

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