Topic: Current Drain
in Forum: C3 Electrical
I have a 1980 Corvette and last Saturday my battery was completely dead. The battery is less than a year old and I had just driven the car a week earlier and the battery was fine. I doubt the problem is in the charging circuit. The battery took and is holding a charge but I have disconnected it from the system. Apparently something is draining the current out of it at a fairly rapid rate when the car is just sitting.
How do I measure for this and what components are the most likely cause? I have a very good Multimeter that I can measure both ohms and current with but don’t really know how to use it for this or where to begin.
Herb
It works for me. I am an old guy too. Stupid queston but how to you test for current drain? Set the multimeter on ohms and touch red to hot and black to ground or set it on current and do the same? Its a great meter but this is one function I have never used.
David - Thanks for the info. I think I am a bit of slow learner here and it has been many years since I had any schooling in electricity. (High School Physics?). I assume when you say put it on amps that is "current" on my meter which will read up to 10 amps on the basic setting and 20 if I am quick to disconnect it. If I put the red probe on the postive cable and the black one on the negative battery post (I assume that is what you meant) with everything off in the car the meter should read "zero" if I have no problems and something more than that if I have a current draining "short". If I do show some current then I start disconnecting fuses till it goes away and that will be my problem circuit. Then go from there to isolate what it is in the circuit.
Sounds pretty straight forward but I just don't want to do something stupid and either fry my meter or something in the car.
Thanks again,
Herb
82 collectorshark is right, a test light is a good tool. It should not light if you don't have a draw. Make sure you pull the fuse for interior lights, makes it easier then trying to hold the door switch.
Denny
Thanks guys. Placing the meter in line to measure current makes sense. I took a long look at the rather cryptic diagram that came with my meter and that was what it showed but it was sure not obvious the first time. It has been a long time since I learned about electricity and all I have ever really done is to measure voltage and resistance (basically just continuity).
My meter has two setting 320ma and 10amp which is fused to 20 if it is brief so I should be fine. Now all I have to do is find the problem.
Looks like I have my weekend project.
Herb H
Thanks everybody.
I found the current drain. The relay from the anti-theft system decided to start working again after many years of most of the system being disconnected. It was sucking up about .17 amps all the time. I unplugged it and WOW - no more current drain.
Herb H