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2007 Mustang V6 Battery Drain Questions

33K views 16 replies 7 participants last post by  Richcat 
#1 ·
Hey guys, I've been here a few times with questions about my S197 V6 and always use these forums for tips and fixes, so thanks for keeping this great community alive.

Main thing worrying me right now is battery drain on my '07 V6. For years already the battery has been dying and losing charge over night, and even when consistently driven daily (especially during the winter time). I've looked into this online and have seen many people with similar problems related to different things, especially the shaker systems (which my car does not have), but haven't found any concrete fix that really helped. I know there has to be something draining the battery, as this has been happening for a while now and because I have gone through at least 3 battery replacements already. Also, by using a multimeter I saw that there was some voltage going through the battery when it was off.

I always make sure to turn everything off when I leave the car (radio, anything plugged in, etc). What I did notice, however, is that the dc car outlet still remains on even when the car is off and the keys removed. I have a phone charger there sometimes, and one time, I left my phone in the compartment by accident and it continued to charge for hours with the car off. I'm pretty sure that shouldn't be happening, and I was wondering what would be the best fix you guys would recommend? This definitely isn't an urgent matter, but I'd like to sort it out after all this time haha. So far the only thing that comes to mind is some kind of complete battery shut off switch to use overnight?

Any recommendations or help at all would be great! Thanks so much! :)

(I also heard of a technical service bulletin on this issue, but haven't been able to find it. If anyone has a link, that'd be great!)
 
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#2 ·
You could start pulling fuses with the meter on the battery to try to determine which circuit is drawing.
 
#3 ·
ive heard of guys having this same issue, but not sure on the fix. there will always be some battery drain, the security system uses power( little red flashing light on the cluster) and ya, the power outlets stay hot. ive left my radar det on over night lots of times, but it doesnt drain the battery. i would still unplug the cell phone. are you using low amp cheap batteries? i`m using a gt size die hard gold, its a bigger battery and you have to remove the plastic side blocks in the tray. ive left the stereo on all day playing while working on the car many times.

i installed a shaker 1000 hu, but i dont have the amps and extra speakers so i dont know about that set up, but you dont have that either. it would be driving me nuts too if my car kept dying. might be worth checking with a auto electric shop.
 
#4 ·
As others have said, could be many things. You have to do the work to locate the problem. And definitely unplug power port items when you shut it off. One problem I discovered last summer was that many aftermarket tunes fail to shut down the SJB properly (just reinforcing my opinion that a lot of aftermarket businesses do things on the cheap), which then continues to draw power and will result in a much shorter vehicle storage time (but not so bad as to be an overnight issue). The maximum Ford battery drain spec with everything off is 50 mA, and the cars are supposed to start after sitting for 30 days minimum, assuming all stock and in proper working order.
 
#6 ·
battery drain 07 v6

I have the same problem with the battery draining. I have taken it to 3 diffent places and had all systems checked. Nothing is found but the Ford dealer said it "isn't happening". However, this figment of our imagination happens everyday! I had to jump it to leave the dealership. There seems to be a bigger issue that Ford doesn't want to deal with or fess up to. We have NO aftermarket adds, no fancy radio, nothing plugged in, no anything but a stock car without bells and wistles. It has to be put on a charger all night and then you can only start it and drive it over an hour and have it restart. But even then if it sits for more than 6 hours it has to be charged again. New (very expensive) battery, altenator checked 3 times. Looked and looked for a drain and can't find where it is coming from. New starter even since the original has too small wire to it and it burned up. It came with a "Ford note" stating it was a manufacturing issue but since it wasn't a "safety" issue they didn't have to pay for the $300 fix. I'm just about to blow it up! Any other suggestions would be great since I still have 2 years worth of payments left!
 
#7 ·
I have the same problem with the battery draining. I have taken it to 3 diffent places and had all systems checked. Nothing is found but the Ford dealer said it "isn't happening". However, this figment of our imagination happens everyday! I had to jump it to leave the dealership. There seems to be a bigger issue that Ford doesn't want to deal with or fess up to. We have NO aftermarket adds, no fancy radio, nothing plugged in, no anything but a stock car without bells and wistles. It has to be put on a charger all night and then you can only start it and drive it over an hour and have it restart. But even then if it sits for more than 6 hours it has to be charged again. New (very expensive) battery, altenator checked 3 times. Looked and looked for a drain and can't find where it is coming from. New starter even since the original has too small wire to it and it burned up. It came with a "Ford note" stating it was a manufacturing issue but since it wasn't a "safety" issue they didn't have to pay for the $300 fix. I'm just about to blow it up! Any other suggestions would be great since I still have 2 years worth of payments left!
If it’s a coupe try putting one of the rear seats down and confirm that the trunk light is going out. A bulb staying on will drain a battery pretty quick. Beyond that, since no one else seems to be able to help (or care to take the time to do their jobs right), invest in a DVM and learn how to use it. As another poster already described, measure the current drain on the battery and then start pulling fuses and relays to try to find the culprit circuit (just be sure you put them back in the right location). Fuse ID’s are in the owner’s book, and wiring diagrams can be found at this link:

Ford Service Manuals - Wiring Diagrams
 
#9 ·
Well I guess the batteries for this model mustang really aren't the strongest. Battery died again, probably didn't help that the cold frosted my car overnight either haha.
I just bought a clamp meter though so hopefully I can find some sort of drain going on. Tried it a second ago after the car sat for 40 minutes, but I couldn't seem to get any reading on the meter besides 0-10 milliamps, but I know that's wrong because I even opened the car door which turned on a light inside and should raise the current in the battery to at least above 100milliamps but I got the same exact reading. Just to make sure, there isn't anything special I need to do with the clamp meter besides zeroing it and clamping the negative cable which connects to the battery right? I know the meter's working because I used it on an air purifying fan which measured at some 650milliamps...

If anyone has any advice, that'd be great :)
 
#10 ·
Not knowing what kind of clamp-on meter you have it’s hard to say, but typically they’re not that accurate much below about an amp, and at less than 100 mA are pretty much in their noise floor. There are specialized ones for lower currents that are designed to plug into a scope or DVM, those are accurate down there, but are usually pretty expensive (and small). I have a calibrated 120 mA source that I use to test my clamp-on after I zero it, sometimes I can get a ballpark reading in the 100 mA range with it on the battery cable that way. If you connect a 100 ohm 5 watt resistor to the car’s 12 volt battery the draw will be 120 mA. Clamp the meter onto one of the wires leading to the resistor and see how accurately it reads the 120 mA. The resistor will get warm, so be careful handling it.

BTW, my 2005's factory battery was replaced summer of '07 and it's still running strong. When everything's right the batteries seem to hold up fine in the S197s. When replacing the battery make sure you get the 40R size, and not the smaller one.
 
#11 ·
EDIT: Thanks for the information about the measurements stars. I just kinda figured it out.

Turns out my clamp meter was working fine, when I checked for drain again, it was still showing 0mA current. This time, I unlocked the car remotely which turns on interior lights plus headlights. This gave me a current reading this time around, not reaching 1amp yet though. I can't get a perfect mA reading though, as the meter only goes to the tenth place which gives 10mA. I guess this means that there is only a battery drain of 10mA or less when the car is idle (which is definitely below the 50mA warning sign).

I guess this means there isn't anything rapidly draining the battery (although I will check again tomorrow morning to see if something turns on and causes a larger drain over time) so the problem must be either the battery(ies) I've been using or the alternator not charging the battery correctly. Am I right in this assumption?

I guess my next plan of action should be to trace the voltage of the car battery before I drive, after, then as the car remains off. Does that sound like a good test for the battery charging?

And also, what recommendations do any of you have for replacement batteries? I'd prefer one at walmart because of their warranties. Is the 40R size a direct drop in replacement for an '07 V6?

Thanks!
 
#12 ·
The Duralast Golds at Autozone are decent, though I don’t think they have them in the 40R size. The Sears Die Hard Golds are also good, and they do come in the 40R size. Mine was replaced at the dealer in ’07 with a Motorcraft 40R and it’s held up fine, not even a hint of corrosion on the lugs. I think it’s just the factory installed Motorcrafts that are junk.

Might want to interrupt the battery circuit by pulling the negative battery cable and using a conventional meter measure the standby current drain. Use a jumper initially across the meter to allow things to stabilize, then remove the jumper so you can take a reading with the meter. A clamp-on that has a minimum value of 10 mA just isn’t going to be accurate down there.

As far as charging voltage, start the car up and have a friend take it up to 1,500 RPM and measure the voltage across the battery, should be between 14.0 - 15.0 volts with everything switched on (lights etc) if it’s charging right.
 
#13 ·
Woah thanks for all the information!

So can you explain checking for drain using a standard multi meter a bit more? I was originally planning on doing this instead of the clamp also, but wasn't sure if I could do it correctly (looking at directions from the service manual). So I need to use a jumper cable between the negative battery cable and post, disconnect the cable from the battery while keeping the circuit with the jumper cable, then use a multi meter in series between the battery and cable? If you could explain it a bit more specifically that'd be great, especially using the meter in series between the battery and cable (I'm not to familiar with this yet).

I'll definitely try testing the voltage also to see if there's anything iffy with the alternator. And I figure it's time to upgrade to a bigger battery, I just wanted to make sure there wasn't too much of an issue on the side of the car before buying a new one only to age it with too much discharging and recharging.
 
#14 ·
It’s pretty hard to do, but if you can maintain the circuit connection with a jumper while pulling the negative cable off the battery then you can take an immediate measurement. If not that’s okay, pull the negative battery cable, then connect it to the battery with a removable jumper. Connect the DMM current and ground inputs (set on an appropriate amps scale) between the negative battery post and the negative ground cable. Wait an hour for the electrical system to go back to sleep all the way (it’ll wake up when power is initially restored), then pull the jumper off one end so the current flows through the meter instead of the jumper. You’ll probably want the meter on a one or two amp scale so the internal shunt doesn’t drop the voltage too much. You should be able to get an accurate measurement of the standby current this way. After taking the reading reconnect the shunt and disconnect the DMM. The reason for the shunt is to prevent any surge currents from flowing through the meter and possibly damaging it (or blowing the internal fuse) when power is initially restored to the car’s electrical system due to capacitors in various circuits charging up. Don’t try switching on any extra loads while the meter is being used to measure, as the currents in active automotive systems can easily exceed the meter’s ratings and blow the internal fuse, or damage the meter’s shunt.
 
#15 ·
Thanks! I'll definitely check for a more specific drain when I get the chance to.

This morning I did a last checkup with the clamp meter. Battery voltage was at 11 after sitting overnight. Drain at that time (before starting) was still less than 10mA. When I started the car and brought it to 1500rpms the voltage was reading 13+ volts. Then when off the battery stabilized at 12+ volts. Still couldnt get any kind of drain reading..

Turns out my battery is more than two years old anyways, so I'll probably replace it anyways. It's an Ever Start branded 40R battery. I guess there isn't much to do at this point.. Maybe invest in a trickle charger or something haha.
 
#16 ·
At 1,500 RPM anything below 14.0 volts could be considered suspicious. You may have an open diode in the alternator resulting in a reduced charging capability and it may not be bringing the battery to full charge when you drive it. A lot of short trips can whittle away at the battery’s charge too. Rule of thumb is that it takes about 20 minutes of freeway driving to recover the lost charge from a single starting event. So short city traffic driving with trips of only five minutes or so can cause a battery to become depleted too. If that’s the case then a trickle charger is one solution.
 
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