Problem with my battery (low voltage reading even well above idle)
04-10-2008, 10:49 AM
#1
Registered User
Thread Starter
iTrader: (1)
Join Date: Feb 2008
Location: Ventura, CA
Posts: 193
Car Info: 04 EJ207 6mt WRX, 08 Spec B
Problem with my battery (low voltage reading even well above idle)
Alright so I was accelarating to get on the highway, and my battery light came on as well as my brake light, plugged in the Accessport when i was driving and saw the battery was reading 11.5 volts so its not recharging, mind you this is the same batttery that came with the car when i bought it new in '04, yes probably needs to be replaced. But maybe alternator as well. Why would the Brake light come on as well? I checked the master cylinder, level is good, the pads were replaced about 10,000 miles ago or so. if the battery has low voltage is there a brake sensor that will click on if it does not send back the correct amount of voltage due to the battery? any advice is much appreciated..thanks
Last edited by jam007; 04-10-2008 at 11:28 AM. Reason: cursing is not professional
04-10-2008, 11:33 AM
#4
BanHammer™
iTrader: (8)
Join Date: May 2000
Location: Wagonmafia Propaganda Lieutenant
Posts: 47,585
Car Info: 2001 Forester RS2 SPEC-F
I would check your alternator as well. When your car is running, you should not be using the battery and your voltage should be well above what you were reading.
04-10-2008, 11:39 AM
#9
BanHammer™
iTrader: (8)
Join Date: May 2000
Location: Wagonmafia Propaganda Lieutenant
Posts: 47,585
Car Info: 2001 Forester RS2 SPEC-F
http://www.econofix.com/alt.html
The alternator or generator keeps your battery charged. It also provides power to run your lights and other electric accessories on your car.
An alternator is an A/C generator. Cars used to have generators, since cars run off DC current. The reason manufacturers went to alternators is that they charge better at low RPM's. The A/C output of the alternator is changed to DC by rectifier diodes in the alternator, so a car alternator really puts out DC power.
Symptoms of a bad alternator include hard cranking, lights that seem too dim, and of course the "BATT" or "GEN" light glowing on the dash.
TESTING
Put a voltmeter across the battery while the engine is running . Voltage should be 14.2 volts. Lower than 14 volts or higher than 14.4 volts could mean a problem. Turn on the lights and accessories: voltage should stay up around 13 volts. Idle engine up to 2000 RPM. Voltage should go up to 14 or so.
NOTE: BAD ALTERNATOR SYMPTOMS ARE VERY CLOSE TO BAD BATTERY SYMPTOMS AND BAD STARTER SYMPTOMS A properly operating alternator cannot charge a bad battery!
An alternator is an A/C generator. Cars used to have generators, since cars run off DC current. The reason manufacturers went to alternators is that they charge better at low RPM's. The A/C output of the alternator is changed to DC by rectifier diodes in the alternator, so a car alternator really puts out DC power.
Symptoms of a bad alternator include hard cranking, lights that seem too dim, and of course the "BATT" or "GEN" light glowing on the dash.
TESTING
Put a voltmeter across the battery while the engine is running . Voltage should be 14.2 volts. Lower than 14 volts or higher than 14.4 volts could mean a problem. Turn on the lights and accessories: voltage should stay up around 13 volts. Idle engine up to 2000 RPM. Voltage should go up to 14 or so.
NOTE: BAD ALTERNATOR SYMPTOMS ARE VERY CLOSE TO BAD BATTERY SYMPTOMS AND BAD STARTER SYMPTOMS A properly operating alternator cannot charge a bad battery!
04-10-2008, 11:40 AM
#11
BanHammer™
iTrader: (8)
Join Date: May 2000
Location: Wagonmafia Propaganda Lieutenant
Posts: 47,585
Car Info: 2001 Forester RS2 SPEC-F
http://wiki.answers.com/Q/How_do_you...ernator_is_bad
constantly dead
your battery is there for starting purposes only- once you start the car, the alternator/generator takes over, and runs the cars electrical system (and recharges the battery)- if you start your car and then disconnect the battery, if your alternator is good, the car will keep running. bad alternator and the car will die. note that if your alternator is bad, your car can run off the battery for a while till the battery dies. sure sign of bad alternator = constantly dead battery.
your battery is there for starting purposes only- once you start the car, the alternator/generator takes over, and runs the cars electrical system (and recharges the battery)- if you start your car and then disconnect the battery, if your alternator is good, the car will keep running. bad alternator and the car will die. note that if your alternator is bad, your car can run off the battery for a while till the battery dies. sure sign of bad alternator = constantly dead battery.
