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Discussion Starter · #1 · (Edited)
What is Resistance Between Battery Cables (with Battery removed)?

Greetings:

I'm trying to troubleshoot a problem with my car's (1991 Legend L Sedan) electrical system.

For some reason, something appears to be discharging my car's battery when the car sits overnight outside. I'm wondering whether a short circuit somewhere within the car is causing the battery to discharge.

Today I took the battery out of the car and measured the resistance between the positive and negative battery cables. The resistance was negligible (somewhere between 0 and 100 ohms). Is this state of affairs normal? I would expect to find an open circuit (viz., infinite resistance) between the cables provided the ignition switch has been turned off.

Does anyone out there know how much resistance there should be between the positive and negative battery cables (with the battery removed from the vehicle)?

Thanks for the info and for your help.
 

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Don't check for resistance, it's not going to get you the information you need. Charge the battery and check for voltage after letting the battery sit a couple of hours. The voltage should be 12.6. Anything less than that the battery is weak or should be replaced.

It sounds like you have a parasitic load draining your battery. Set up your volt meter to check current. Dissconnect one battery terminal and connect the meter in seres between the cabel and battery. You should not see more than 1/10 of an amp. Any more than that then you have a problem. (NOTE: DO NOT TURN ON KEY WHILE TESTING THIS AS YOU WILL BLOW THE FUSE ON YOUR METER).

If you have a parasitic load then you can pull each fuse until the load drops off, so you can find which area is your problem child. Once you find it then you will need to get a wiring diagram of that circuit and check all in that circuit.
 

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to check for surface discharge over battery...

unhook battery(if you have stock cd player be careful), Hook up the meter negative lead to negative battery post and positive lead to positive post..What do you get?? It should be 12.65 but anything over 12.45 should be good, if it is over 12 it should be fine and get you through for a while.

Anyways, now put he the negative lead near the the terminal and move across the plastic top, if you are still getting high voltage that means you have a surface discharge. Clean the battery off and be careful not to get anything like baking soda under the maintanance caps if you have them.

good luck.
 

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Discussion Starter · #5 ·
Problem Solved: Shorted Rear Power Antenna

Greetings:

Having received considerable assistance from the members of this Forum, I'm writing to report that I successfully identified the part responsible for my battery drain. About three weeks ago, my car's rear power antenna (a three-year-old aftermarket unit manufactured by Hirschmann) stopped working. I didn't think much of it at the time, reasoning that the antenna's motor had burned out. The car's battery didn't go dead until a week or two later. At the time, I did not connect these seemingly unrelated events.

When I performed a battery drain test on my Acura yesterday, I discovered that Fuse 56 in the underhood fuse box was drawing a tremendous amount of current (with the car turned off). (The current was strong enough to blow a 1-Amp fuse on my voltmeter.) Fuse 56, I learned from the Service Manual, controlled, among other electronic devices, the rear power antenna motor. A light-bulb went off in my head at that point--for the first time linking the earlier dead power antenna with my car's dead battery. I removed the antenna from the car's circuitry and, lo and behold, no battery drain.

Problem solved--thanks to the helpful folks of this Forum. Had I not learned from the Forum how to perform a battery drain test, I would never have solved this problem--and would probably have had to pay a mechanic lots of $$ to reach a solution.

My thanks to everyone who helped.
 

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Dmulyer:

Do the same as above. When you put an amp meter in series with the negative cable make sure the doors are closed and there are no known loads on. Start pulling fuses until the load drops. You will have some small load on the system from keep-alives and memory.


Dave
 
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