One turned out to be leaky diodes in the alternator (there is no fuse between the big stud on the alternator and the battery positive pole (only a "fusible link"). I have had a parasitic leakage problem in several vehicles and airplanes over the years.
In all cases, start at the 10A setting and work down. You might have to switch the meter to a lower DC full-scale current setting to accurately measure the leakage. If the current is over 10mA (0.01A), you have a problem you need to track down. The parasitic leakage current that was formerly flowing through the battery connection is now flowing through your meter, without breaking the circuit as the cable was disconnected from the battery. While holding both probes in place, break the connection from the battery cable to the battery pole. Hold the black meter probe on the outer part of the positive cable connected to the battery. Hold the red meter probe on the positive battery pole. Set your multimeter to DC AMPS, 10A scale. Loosen the battery cable on the positive pole of the battery, but leave it connected. Now I'm really confused as to why the ac amps were too much for the dc amps reading.Ĭlick to expand.First, if you accidently short-circuit a good, fully-charged car battery, it is capable of supplying more than 2000A!!! It will usually vaporize whatever causes the short. A car battery is advertised as having 300 cold cranking amps. Since I'm around to learn from my mistake I would really appreciate an explanation.ĮDIT: Come to think of it. I know I shouldnt have done that, but I don't understand why. Turns out there isn't even a 10A a/c setting for this multimeter.ġ) Why did the arc jump to the other lead instead of completing the path through the multimeter?Ģ) Why is 10 amps of AC different from 10 amps of DC when it comes to taking a reading with a multimeter. I was surprised that the power didn't shoot through the meter and blow it up. A nice arc shot from one lead to the other as soon as I when from the hot to a grounded screw. Well, you know what happened, I had the multimeter set to 10ADC. So, like a goofball I decided to see the reading on the a/c wall outlet thinking o ya, this circuit is 15 amps. I know I've been able to get around 14 amps from the car battery when when the car is running which shows that the alternator is doing its job well.
But none of the fuses being out stopped the draw.Īnyways, what I did was I set the multimeter to 10 Amps. Pulled all the fuses one by one to see which one would cause the light to shut off. The 12VDC test light connected from the positive battery post to the positive cable(after pulling cable off) shows that there is a draw which causes the test light to come on. Battery has been dieing if I leave it connected for a few days. I was about to go out to the car to check how many amps were being drawn from a parasitic component in the circuit.