batery drain...

[Cardsfreak]

Hi, I have a 1991 240sx and it drains the batery. I took all the fuses out of the fuse box under the steering wheel, and unpluged the negarive from the batery. Now with and electrical tester I touched the negative lead and the negative wire and I got like 12.3 volts, so I started taking the fuses next to the battery, and I found that the one cousing all the trouble is the one that says "fl75a/alt" I did unhook the connection that I think its the possitive from the alternator, and unplugged the lil connction on the side, and I still had 12.3 volts. Also when I remove this fuse nothing in the car works, not the clock, not the stereo, not even the lil anoying "ding...ding...ding" when you leave the key in the ignition. And if I remove that fuse I still read 7.9 volt with the electrical tester and thats beeing caused by the fuse "fl25a/Eng cont"...any help on how I can find the problem and/or fix it it would be very apreciated.

[vancouverbc]

When you disconnect the 75 amp alternator fuse, the drain goes from 12.3 to 7.9? and when you disconnect the 25 amp fuse the drain goes from 7.9 to zero? the 25 amp goes to the eccs relay. this relay is green and is in same box as the 25 amp fuse. the alternator fuse goes to several places but most places are fused. The accessory relay number 2 is not fused.

I tested between the negative battery post and cable and got 12.3 volts on my car. I measured milliamps and got around 26(it started at 70 and came down). The electronics in the car does this. 26 milliamps is ok which is consistent with my battery being good. I pulled all the relevant fuses and it changed nothing. Lesson: measure in milliamps. This is on any cheap volt meter.

I was getting 5 volts with the battery totally disconnected so the electronics does weird stuff and volts can be misleading.

http://www.exide.com/products/...d.pdf

Modified by vancouverbc at 7:33 PM 4/22/2007
Modified by vancouverbc at 7:36 PM 4/22/2007

[Cardsfreak]

Thank you for your answer...Did you get that reading with the key off the ignition and the doors shut?, and yes, if I take the 75 amp fuse it goes down to 7.9, and if take the 25 amp fuse it goes down to zero. and thank you for the link, I read that one already tho. Any help as how I can find the short? if I leave the battery hooked for a day it dies.

[vancouverbc]

Key was out of ignition but Im not sure about door. I got 12.3 v with all the fuses and relays out of the relay box. Tracing a short can be a big job if you dont get lucky. Look for nicked wire and cut wire. I would take some milliamp readings to find out which part of the circuit is the problem. (instead of volts). You need a wiring diagram . You can test a hot wire for voltage drop. The reading should be zero volts if there are no shorts. or you can look for resistance in a dead wire. That link you mentioned is about the only attempt i have ever seen made to explain this subject.