[CHIODI]

still having the same problem...battery dying after a few days. may be intermittent.

where do i begin with this problem? is there a common trouble these cars have?

someone mentioned a computer relay? where is it and where do i get one?

thanks!

[Chris951]

I would start by getting the battery AND alternator tested.

[ryanw]

check the light on the sun visors, it may not be fully shutting off.

pm foggged306, he has a good method of checking and explains it vary well, i was going to attempt to explain but i dont think id do a good enough job.

[ryanw]

Originally Posted by fogged306 Either use a multimeter with a 10A ammeter setting, or a single wire test light with a light bulb in it. You undo the positive terminal of the battery and put your test light or meter across the battery lead and the battery terminal so it completes the connection through the meter/light. Then start pulling fuses and unplugging aftermarket equipment one by one until the draw goes away. With an ammeter you want about 50mA or so at rest with no dome lights on or anything else. With a test light, the bulb will be lit when there's a draw. How bright the bulb is lit is how severe the draw is. As soon as you pull the fuse for the draw the light on the bulb will go out. This way will narrow it down to the circuit you need to be checking... Also if you have vanity mirrors in your sunvisors, check those. Both of mine went bad and the lights would stay on even with the lids closed and the visor in the up position.

here i found it in another thread and this is where i got it Something is killing my Battery!!

[CHIODI]

Thanks ...this is my second battery. I will try pulling fuses. I noticed the needle on the voltage guage drop suddenly at times. I don't think its the alternator since the battery dies when the car is off. It's fine when the car is on although the lights go dim at a light but I think I may have undrive pulley. The volts go anywhere from 12 to 14 volts while the car is on.

[CHIODI]

can i check for shorts at the fuse box by removing the fuses and going across each fuse socket with a test light?

[fogged306]

Voltage shouldn't fluctuate that much when the car is on. Should read between 13.8v and 14.4v while running w/o lights or heat ect. on.. If it drops below that with no accy's on, then you have an issue somewhere in the charging system. Voltage regulator, alt itself, or possible poor connections somewhere. Start there first.

Yes you can check for shorts like that at the fuse box, as long as you have a single wire testlight. Just remember that if you do that kind of testing, the domelight fuse will show a draw because it's on (unless you climb in the car and test with the door shut). Done it that way once or twice and during the day when you don't notice the dome is on, it's easy to forget and think you've found your issue when you test the fuse for the circuit the light is on.

[CHIODI]

FOGGED thank you man...i will have a look at things tomorrow. i have more questions...can a bad alternator cause the battery to die even when the car is off? could a short circuit cause the fluctuations in the foltage when im stopped at a light? where is the voltage regulator?? thanks

[CHIODI]

also i put a test light between the negative cable and the negative battry terminal and it lit up really bright. am i doing something wrong? should i put the test light between the positive lead and the positive terminal? thanks

[fogged306]

Either way should work, opening the positive or negative connections at the battery will yield the same result. When you did that, you had everything off in the car including the domelight correct? If so, then you definitely have a draw.

Yes a bad alternator can kill the battery even when the car is off. I'm not entirely sure what goes bad in them, but there's something that can cause a pretty substantial drain when it goes bad, I want to say it has to do with the diode trio. I've seen it happen to a few people on the forums but never had any experience with that happening myself.

Yes a short can drop your voltage like that if it's a an intermittent issue with something. Something that severe and happening that often would definitely be causing some burns somewhere though. Are you using a multi-meter or just the gauge on the dash to tell the voltage? If the gauge, don't go by that until you get a meter on there and read the actual voltages. Gauges can give false readings.

I'm not entirely sure what year they switched, but some mustangs had an internal voltage regulator and some had an external. I want to say 86 and before had the external and 87-up were internal, but I'm just going on memory. Maybe someone else can give you that info that knows for sure.

[CHIODI]

Fogged thanks again. hey i just spent about five hours trying to figure out where this short is. i still have a short but i narrowed it down a bit. i get a short on circuit 18 in the fuse box...that fuse is for a lot of things. i also opened up the junction point on the fender under the hood and found the yellow wire to have the short. any ideas??

[CHIODI]

[fogged306]

I couldn't tell you what that fusible link is for just by looking at it. That almost looks like it could be an aftermarket one because none of mine looked like that on my car. When you pull that link off, does fuse 18 still get powered up? ... Just a guess here, but the only thing I know of that has multiple wires like that on one fusible link would be power feeds to the EEC. Maybe check the EEC power relay in the passenger kick and make sure it's not staying on with the ignition off.

As far as narrowing it down in circuit 18 itself, this is where having a multi-meter helps. Depending on how many mA of current the draw is, is where you could start looking. If it was a larger drain, start at the compressor clutch, smaller one, unplug the cluster and seatbelt chime wires. The way I do it is to just keep the process of elimination going annd start unplugging things one by one.

[CHIODI]

hi fogged. i am using a test light. when i go up on 18 in the fuse box the continuity light comes on. when i touch a ground and the yellow lead the continuity light also comes on. this happens even with the battery disconnected and the computer relay unplugged. where is the compressor clutch plug? my car doesnt have AC. where are the seatbelt chime plugs etc? sorry for being such a pest but i really want to solve this problem and you seem pretty knowledgeable. where in NY are you anyway? im in westchester county

[fogged306]

Was that yellow wire connected to ground or to 12v? If it was connected to 12v and you went to ground with the testlight, then you're just getting some kind of backfeeding.

Did your car not have A/C to begin with or has it been removed at some point? If it's been removed, the wiring is probably still there. The compressor clutch wiring would be on the passenger side of the engine harness if I remember right. Should be a 2 pin plug with about 16 gauge wires.. Again just going off memory here because I removed mine from the harness when I rewired my engine bay. Seatbelt chime wires will be more than one connection. Not sure where the chime is actually located, but the wires for the trigger for the chime will be in the seatbelt clip itself. Should be a plug under the seat or under the carpet that's under the seat.

It's really hard to give advice on an electrical problem over the internet. I could track it down if I was working on it myself, but to give a step by step on what to do next is very tough to do, so take what I say as just suggestions because I could be leading you down the wrong path and not realize it... I'm about 8hrs away from you near Buffalo. To bad too, If you were close I would say come over to my shop. I could probably pin down that draw in less than an hour for you.

[CHIODI]

ok ill go look at things again man thanks....funny thing is that the car runs fine. all the guages, the chimes, the electric fan...everything. it seems to come and go. my trunk lights dont light up and i have an aftermarket radio but i dont think that has anything to do with it.....

[CHIODI]

hi Fogged now im really confused. i bought a multimeter and put it on the ma dc and there is a .17 draw which i think is ok....what is going on? also i put a continuity tester on the battery leads without them being hooked up and it lights up. is that normal? thanks.

[fogged306]

Are you on the "A" setting or "mA" setting? If you were on the DC A setting, that would mean 170mA which is over a hundred milliamps too much. If you were on the mA setting, then you're getting less than 1 milliamp, which is probably unlikely. I haven't done a current check on what these computers draw at rest, but it will most likely be a few milliamps, not less than one. Most newer cars with computers that need to stay "alive" will draw between (roughly) 20mA and 50mA with everything off in the car.

If I'm honest, I've never tried putting a continuity tester across the cars battery leads so I'm not too sure if that's normal or not. There may be some circuits in the car that will show a short because they have very little resistance to them so I wouldn't really go by that. The ammeter feature of the multimeter is going to be much more useful in tracking a current draw.

[CHIODI]

hi Fogged i went over everything and all seems ok. i did another check for draw with my multimeter and it read 17 ma which i think is normal. is it? I also reemoved the aftermarket stereo but i dont know if that has anything to do with my problem. i have yet another question...if the draw is fine what other issue could kill the battery other than an inermittent issue? THANK YOU!!!

[fogged306]

Yea 17mA won't kill your battery very quickly. Just to double check, hook your stereo back up and check the draw again. I've seen stereo components go bad a few times and kill a battery.

A weak charging system can leave a battery near dead and at that point 17mA will be enough to kill it overnight. You said you had sporadic voltage fluctuations before, so I would look at the alternator now.

Also, car batteries need to be trickle charged for a few days after they're drained completely to bring them back to fully charged. Just a jump and a some drive time isn't gonna do it, so you may already be leaving your battery in a constant weakened state.