Naptown Dave Posted August 15, 2013 Share Posted August 15, 2013 Guys I have a '75 280Z with an LS swap that is draining the battery over night. The car is not complete and will start and run but has not been ran for any amount to time. I have 2 maxifuses feeding two fuse panels, one for the engine/ecm and one to the factory fuse panel. I have checked both maxifuses for draw and to one feeding the factory panel is drawing the power. I have current flow through the cig lighter fuse and the brake light fuse. The cig lighter is not in the receptical and the rear harness is not hooked up. Are there any common areas that have caused problems with battery draw? I have searched and see some references to the brake warning causing draw,would that be an issue because the wire to the brake pressure switch in the engine compartment is not hooked up? Why am I seeing draw through the cig lighter fuse? Quote Link to comment Share on other sites More sharing options...
jhm Posted August 15, 2013 Share Posted August 15, 2013 Are you sure that there's nothing else wired into the cig lighter hot line? That's often used as a convenient 12V source for accessories like a stereo, electric fan controller, etc. Try pulling the fuse to see if anything else besides the cig lighter is affected. Also....not sure what alternator you're using, but I've seen cases where they can be wired improperly so as to draw current even when the ignition is 'off'. It doesn't affect their operation while the engine's running, but they run the battery down quickly after the engine's shut down. Good luck tracking down the culprit. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 15, 2013 Author Share Posted August 15, 2013 Jhm I will double check the cig circut but I believe I've pulled all the makeshift wiring the PO had installed. I bought this car without an engine so I have no idea what condition the electrical was in when last ran. There was wiring ran from the engine compartment to the fuel pump, but that was removed and the fuel pump is controled/fed from the LS fuse panel. The alternator is the factory LS so it only has one control wire, controlled by the ecm. The LS/Datsun wiring intergration went well without any drama so I have to expect some gremlins to pop up! Thanks, I'll post what I discover. Quote Link to comment Share on other sites More sharing options...
rsicard Posted August 15, 2013 Share Posted August 15, 2013 While measuring the current drain, disconnect circuits connected to the fuses. Disconnecting one will yield zero current drain. That is the culprit. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 15, 2013 Author Share Posted August 15, 2013 I set my meter to mV and tested across the fuses, I believe that does the same thing without pulling the fuses. I'll try to check the amps across the open fuse poles too just to make sure. Quote Link to comment Share on other sites More sharing options...
ihiryu Posted August 15, 2013 Share Posted August 15, 2013 Disconnect the power (or ground lead, doesn't really matter), hook up a multimeter in between the battery and battery cable. Set the multimeter to amps. Generally speaking, you should only have a drain of .05 or so. Some cars allow higher than that. Slowly disconnect fuses and once the drain goes away that's you're culprit. If you pull the fuse and the multimeter doesn't change, make sure you plug it back in and move on to the next one. But since you're using a maxi-fuse, I tend to think you've got more than one circuit on the maxi-fuse. If that's the case, then you'll have to manually disconnect power from them one at a time. The brakes should always have power. The cigarette lighter is 50/50. A lot of american/older cars generally have cigarette lighters that were constantly on, mine never worked on the Z, so I never bothered with it. Think about it this way, if a car died, or had a failure with the igniton switch (240sx have this issue) where the car just shuts off, and that person goes to brake, but the brake lights never shut off...oh my, think of the havoc it'd create. The problem is that you don't have a short, believe it or not, I'd much rather find a short than a crossed lead. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 15, 2013 Author Share Posted August 15, 2013 Yeah I think a short would be way easier to track down. I have 2 maxi fuses one for the ecm , fan and fuel relay power and a relay power to the starter solenoid controlled by the Dat start signal wire. The other one feeds the factory fuses. I ran new wire to the fan and fuel pump. Everything under the dash is connected but the front and back harnesses are totally disconnected. If someone has a list of what is supposed to be hot with the key off that would be helpful. Quote Link to comment Share on other sites More sharing options...
Domzs Posted August 15, 2013 Share Posted August 15, 2013 Components that can be turn on with key off should be hot all time , like brake switch , park/head lights , cig. lighter (?) . How many amps is your draw ? Also try to disconnect your alternator wirings to see . Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 15, 2013 Author Share Posted August 15, 2013 Looks like the fuse on my amp meter is cooked. I'll have to get another one tonight or tomorrow Quote Link to comment Share on other sites More sharing options...
Domzs Posted August 16, 2013 Share Posted August 16, 2013 (edited) Looks like the fuse on my amp meter is cooked. I'll have to get another one tonight or tomorrow You can use an old school test light for testing . I use an amp probe when I check for draw at my shop because most newer cars have BCMs and other modules that stay awake for a long time , sometimes up to 45 min. Edited August 16, 2013 by Domzs Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 16, 2013 Share Posted August 16, 2013 (edited) I have searched and see some references to the brake warning causing draw,would that be an issue because the wire to the brake pressure switch in the engine compartment is not hooked up? The brake check warning lamp relay is powered off of a yellow wire from the external regulator in the stock configuration. If you or someone did some rewiring at the old regulator harness that could be the source. Easy to check, the relay will click and there will be a small spark at the negative post when the battery cable is re-connected. Take the cable off and put it back on a few times, listen and look. The relay is under the passenger seat. The brake pressure differential switch lights the lamp but shouldn't cause a draw if disconnected. Edited August 16, 2013 by NewZed Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 16, 2013 Author Share Posted August 16, 2013 No relay click when I attach the battery cable, I do however get a pretty solid spark. I do hear a relay pull when i turn the ignition to run. I picked up a decent multimeter to replace the $7.99 special so i'll check my amp draw. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 16, 2013 Author Share Posted August 16, 2013 This solution is so ground breaking it may have to be a sticky. Apparently the dashboard lights draw 1.46 amps even if they are turned all the way down so you can't see them in normal shop lighting. I reached over to make sure the key was in lock and noticed the headlight switch was on. Thanks for the tips guys, I'll try to remember to check the obvious first! Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 16, 2013 Author Share Posted August 16, 2013 (edited) Double post Edited August 16, 2013 by Naptown Dave Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.