battery light on

[daveid]

I have an 86 honda accord and about 2 months ago i replaced the alternator and the battery light is coming on again. The alternator is good and the battery is brand new and pushing 13 volts too. I changed one of the wires from the side screw to the top screw on the battery terminal connector, but i dont think that makes a differance. The battery doesnt come on until i hit about 2500 rpms and if i dont hit 2500 rpms then it flickers on and off but i dont get any power loss, so im really stumped. Any help?


Thanx

[sracing]

Originally Posted by daveid

I have an 86 honda accord and about 2 months ago i replaced the alternator and the battery light is coming on again. The alternator is good and the battery is brand new and pushing 13 volts too. I changed one of the wires from the side screw to the top screw on the battery terminal connector, but i dont think that makes a differance. The battery doesnt come on until i hit about 2500 rpms and if i dont hit 2500 rpms then it flickers on and off but i dont get any power loss, so im really stumped. Any help?


Thanx

It's not a real sophistocated circuit. The "battery" lamp is simply wired in series with the field coil of the alternator. The alternator is excited and regulated by this field current. If the lamp is coming on, it indicates that the alternator is requiring excessive field current to provide the normal output voltage.

An open diode(s) in the alternator can do this, a battery with shorted cells or some form of short circuit.

Using a good volt meter turn everything off in the car and measure the battery voltage. It should be 12.6 -12.7 volts. Now start the car and turn the headlghts, a/c, etc on. Measure the battery voltage. It should be 13.2 or more volts depending up on temperature. etc. If it is still 12.7 or below you have a defective alternator. You MIGHT have to race the engine slightly above idle to get the 13+ volts, but if you have to race it more than 1000 RPM to get it there, it's bad.

Try the above, but it sure sounds like you got a bad alternator based upon symptoms.

Jim
SR Racing

[daveid]

well i have a digital multimeter and it reads 1.2 when the cars running with out anything on. so ill try it with everything on and see what it goes to. im just pissed cuz i just got a brand new alternator and battery. I think its the battery though only becuase when my alternator went bad, the car would only have juice for about five days and then die and this time my car has been going for like two weeks and still going the same as it did the day it went on. so im stumped. but ill check those volts. thanx for the help

[sracing]

Originally Posted by daveid

well i have a digital multimeter and it reads 1.2 when the cars running with out anything on. so ill try it with everything on and see what it goes to. im just pissed cuz i just got a brand new alternator and battery. I think its the battery though only becuase when my alternator went bad, the car would only have juice for about five days and then die and this time my car has been going for like two weeks and still going the same as it did the day it went on. so im stumped. but ill check those volts. thanx for the help

I assume you mean tht it read 12 (not 1.2). A fully charged battery should read about 12.7 with nothing on, about 12.6 with a slight load. When running it should be over 13 with load or not.

Jim
SR Racing

[daveid]

no it says 1.2 and it says that 1.5 means fully charged and 1.0 means dead. but i didnt know that thats what i was buying, i thought itd be just like a regular one but just digital.

[MagicRat]

Originally Posted by daveid

no it says 1.2 and it says that 1.5 means fully charged and 1.0 means dead. but i didnt know that thats what i was buying, i thought itd be just like a regular one but just digital.

Thats correct, a digital one does work like an old-style analog one, it's just more accurate.
Are you sure the setting is on the right scale, for DC volts? Maybe you have it in thousands of ohms or something.
Try to get an accurate reading, the volts should show something like what sracing posted, and let us know.

[sracing]

Originally Posted by daveid

no it says 1.2 and it says that 1.5 means fully charged and 1.0 means dead. but i didnt know that thats what i was buying, i thought itd be just like a regular one but just digital.

Ok, it sound like you have bought some kind of battery checker, not a digital volt-meter. Assuming that is the case and your meter is working correctly, your battery is not reaching full charge. The reason for this is that it is bad OR, the alternator is not able to put out full charge.

Do the tests I mentioned and/or take it to get a free charging circuit check at a Pep Boys, Auto Zone, etc.

Your alternator is bad, I suspect.

Jim
SR Racing