Short version: I recently had to buy a new battery for my S13 due to the old one being run dry one too many times. It was occasionally draining fast overnight and sometimes would go for days without losing charge. I suspect my amateurish job of wiring underbody lights. The alternator and charging system are fine, according to a mechanic. I haven't had any problems since I've disconnected my underbody lights.
Here's how they're wired: 1 wire comes from positive battery terminal and goes to a fuse and then a switch in the dash. From there it splits at various points and goes to each light. The negatives from each light bar all go back to 1 line connected to the battery negative terminal (I don't think this is necessary, but this is how the instructions said to do it—can't I just ground them? If so, would that be better/safer?). They function as expected, on/off with the switch.
Here's the test I HAVE done: I disconnected the lights from the battery (both wires) and tested the continuity (to check for a short). The thing remained at "open." What does that mean? The switch was on and the fuse was fine, by the way.
I have a multimeter, but I don't know how to test this circuit. =/ Please help! Thanks!
-Darwin
How to test a culprit circuit for battery drain?
"Open" means that there is NOT a short between the terminals. Now here is the trick, a typical multimeter continuity check will only trigger on a very low resistance level. I will have to find my instructions, but certainly less than 100 Ohms. A more subtle drain on the batter will not trigger the continuity check.
Actually, if the continuity check triggers between the two battery terminals I would be shocked that the battery didn't catch fire.
For now, leave the lights unplugged and see if the problem continues.
Further, did you place the fuses near the battery BEFORE the cables passed through any firewall or over any sort of metal that could cut into the cable? I am going to my fiancee's tomorrow to cook her dinner, if I have time after I will start up ORCAD and draw some diagrams, see if we are on the same page.
Edit: I thought on the matter some more, and realised that if you place the multimeter probes across the battery terminals and measured resistance, you SHOULD get a low reading. Not low enough to trigger a "Closed" on the continuity test, but the resistance should be fairly low. I forgot to take into account the internal resistance of the battery. I will explain better tonight.
Modified by dfw240_EE at 3:17 PM 8/15/2005
Actually, if the continuity check triggers between the two battery terminals I would be shocked that the battery didn't catch fire.
For now, leave the lights unplugged and see if the problem continues.
Further, did you place the fuses near the battery BEFORE the cables passed through any firewall or over any sort of metal that could cut into the cable? I am going to my fiancee's tomorrow to cook her dinner, if I have time after I will start up ORCAD and draw some diagrams, see if we are on the same page.
Edit: I thought on the matter some more, and realised that if you place the multimeter probes across the battery terminals and measured resistance, you SHOULD get a low reading. Not low enough to trigger a "Closed" on the continuity test, but the resistance should be fairly low. I forgot to take into account the internal resistance of the battery. I will explain better tonight.
Modified by dfw240_EE at 3:17 PM 8/15/2005
Re: How to test a culprit circuit for battery drain? (Yorb)
to test a battery drain do this: take your multi meter and put it on Amps. take off the positive battery cable. put one lead of the multimeter on the positive battery post and one on the cable end. if it reads more that .05 amps you have too much parasitic loss. to diagnose this have a friend( or whoever you have to pay to help you) start unplugging fuses one by one. when the amp reading drops to around .05 amps you have found the circuit that has the problem. from there you need to see if something isnt turning off, has a bad ground or short, etc. good luck
Re: How to test a culprit circuit for battery drain? (travis newberry)
Make sure the meter is fused!!travis newberry wrote:to test a battery drain do this: take your multi meter and put it on Amps. take off the positive battery cable. put one lead of the multimeter on the positive battery post and one on the cable end. if it reads more that .05 amps you have too much parasitic loss. to diagnose this have a friend( or whoever you have to pay to help you) start unplugging fuses one by one. when the amp reading drops to around .05 amps you have found the circuit that has the problem. from there you need to see if something isnt turning off, has a bad ground or short, etc. good luck
Re: How to test a culprit circuit for battery drain? (dfw240_EE)
if you are using the meter to check a battery drain it shouldnt be that much amps, its not like you are going in series with the starter and cranking it... but yea, never a bad idea...
check your alternator. if the alternator is not keeping the battery charged, the battery will die rather quickly, as it is not designed to power the entire car for long periods of time.
definatly make sure you have a fused multi-meter, its a safety issue.
your lights sound fine, although i would personaly have wired them through a fuse if i was to ever put any accesory on my car like that.
as far as grounding, they can be grounded to any metal surface on the chassis.
definatly make sure you have a fused multi-meter, its a safety issue.
your lights sound fine, although i would personaly have wired them through a fuse if i was to ever put any accesory on my car like that.
as far as grounding, they can be grounded to any metal surface on the chassis.
Re: How to test a culprit circuit for battery drain? (travis newberry)
I know, but I just wanted to do a "stupid reminder" thing. Hate for you to use the unfused terminal and accidentally drop a lead somewhere bad.travis newberry wrote:if you are using the meter to check a battery drain it shouldnt be that much amps, its not like you are going in series with the starter and cranking it... but yea, never a bad idea...
Re: How to test a culprit circuit for battery drain? (dfw240_EE)
yea, never thought of dropping a lead... good call
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Yorb
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Sorry for abandoning this thread... I wasn't getting email notifications for some reason. Hm.
Anyway, so I wasn't having any problems, but I found a section of wire on the positive underbody circuit side before the fuse that had a tiny cut in it. I taped it up and reconnected everything, and have had no problems since. I'm hoping that I'm not slowly killing my new battery. =)
Thanks for the testing suggestions, I will definitely give them a try if I ever have any more trouble with it.
And as for the fuse, it is in the passenger compartment (past the firewall) and actually the wire is in a horrible place (hah)...it goes around the front of the engine compartment and up under the fender lip, and then it dives down into that hole and above the wheel well plastic, then through a tiny place in the foot room of the driver's side. Then there's the fuse, then switch, then the lights.
I know, know. But heck, drill through a firewall? I couldn't be troubled. Besides, this runs right next to the siren wire for my alarm, and I've had no problems with that for years.
Anyway, thanks again. =)
Anyway, so I wasn't having any problems, but I found a section of wire on the positive underbody circuit side before the fuse that had a tiny cut in it. I taped it up and reconnected everything, and have had no problems since. I'm hoping that I'm not slowly killing my new battery. =)
Thanks for the testing suggestions, I will definitely give them a try if I ever have any more trouble with it.
And as for the fuse, it is in the passenger compartment (past the firewall) and actually the wire is in a horrible place (hah)...it goes around the front of the engine compartment and up under the fender lip, and then it dives down into that hole and above the wheel well plastic, then through a tiny place in the foot room of the driver's side. Then there's the fuse, then switch, then the lights.
I know, know. But heck, drill through a firewall? I couldn't be troubled. Besides, this runs right next to the siren wire for my alarm, and I've had no problems with that for years.
Anyway, thanks again. =)
the fuse should be as close to the battery as possible. you should move it before you catch your car on fire.
about the "open" you got... i know it sounds stupid, but was the switch on? if not, of course it will be open, that's the point of a switch. if you did the contunity check again, tough it doesn't sound like you have to, check between the positive lead and the metal of the car. that way yo would get a "closed" if the circuit is grounding out somewhere it isn't supposed to.
about the "open" you got... i know it sounds stupid, but was the switch on? if not, of course it will be open, that's the point of a switch. if you did the contunity check again, tough it doesn't sound like you have to, check between the positive lead and the metal of the car. that way yo would get a "closed" if the circuit is grounding out somewhere it isn't supposed to.