I have recently purchased a battery for my 91 civic si and for some reason the battery light keeps lighting up and when its on idle, u can feel the power getting drained out of the battery itself. Is there a way to check if the alternator is not doing what its supposed to???

 

Start your car and remove the battery while your car is running. If it dies then the alternator is bad.

 

try that and also take it to a local auto parts store like discount auto parts. They have a machine that can test your battery and your alternator for you.

 

NO DONT DO THAT!!!! that is not good for the car to remove the battery while its running. yeah back in the old days when cars that were carbed and didnt have a computer to direct everything you could do that. as for now you can kill your computer dooing that and fry other **** while your at it. for example pretty much all 99 and up caddys will all kill the computer f you do that. its not a good way to test your alt take it to the auto part store and let them use their equipment that was designed to check for that

 

Hmm, I have done this test with all of my cars and I haven't had any problems removing the battery while running. I'm not saying you're wrong, just saying I've never heard of it before.

 

most likely your alternator is bad. take it out, have it checked at a place like autozone. it should give you 13V steady, if less, replace it.
Stan

 

"Hmm, I have done this test with all of my cars and I haven't had any problems removing the battery while running. "

as have I, on several occasions on 2 separate cars. Both ef's.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Home Skillet &raquo;</TD></TR><TR><TD CLASS="quote">Start your car and remove the battery while your car is running. If it dies then the alternator is bad. </TD></TR></TABLE>

Your never suppose to do this, you can cause a voltage spike and fry things. As far as testing the alternator, here ya go.

TESTING
Voltage Test
Make sure the engine is OFF, and turn the headlights on for 15–20 seconds to remove any surface charge from the battery.
Using a DVOM set to volts DC, probe across the battery terminals.
Measure the battery voltage.
Write down the voltage reading and proceed to the next test.
No-Load Test
Connect a tachometer to the engine.
CAUTION
Ensure that the transmission is in Park and the emergency brake is set. Blocking a wheel is optional and an added safety measure.


Turn off all electrical loads (radio, blower motor, wipers, etc.)
Start the engine and increase engine speed to approximately 1500 rpm.
Measure the voltage reading at the battery with the engine holding a steady 1500 rpm. Voltage should have raised at least 0.5 volts, but no more than 2.5 volts.
If the voltage does not go up more than 0.5 volts, the alternator is not charging. If the voltage goes up more than 2.5 volts, the alternator is overcharging.
NOTE: Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.


If the voltage is within specifications, proceed to the next test.
Load Test
With the engine running, turn on the blower motor and the high beams ( or other electrical accessories to place a load on the charging system).
Increase and hold engine speed to 2000 rpm.
Measure the voltage reading at the battery.
The voltage should increase at least 0.5 volts from the voltage test. If the voltage does not meet specifications, the charging system is malfunctioning.
NOTE: Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

 

the "battery" light is not really an indicator of the condition of the battery, its really the "charge warning light" as its called in the owner and service manual. it turns on when the internal voltage regulator is not recieving enough voltage from the alternator. so when the "charge warning light" comes on, it means check the alternator, not the battery. check the alternator using a simple voltmeter and checking the voltage between the top post and ground. should read 14.5 or around there.

as for whether disconnecting the battery or not is ok for the engine, ive done it many times, but the concerns are valid. but overall, its a poor method of testing, because it could only be means of confirming what you should already know when the charge warning light comes on and the alternator is bad, and it may still not tell you anything because the alternator might be putting out enough voltage to run the car, but not charge the battery. so its not a proper test anyway.