Battery Drain

[P M]

For the second time in a couple of weeks the battery has drawn down on my 08 ST. Battery checks good, charges fine. It is apparently intermittently drawing too much while sitting. I went through checking the amps while pulling every fuse. The one that made a difference is labeled BATT1. With that one pulled it drops to .005 amps, which from what I have read is about right. Otherwise it draws ~.286. Can anyone tell me what the BATT1 fuse ties to that could be causing the draw?



Basically, I notice it will be a bit slow to start and will get progressively worse over 2-3 days until it wont start (this is the second time its gone through this sequence, was fine for a couple of weeks in between). Yesterday, it barely started when I left work. Once I got home, I turned it off and it restarted completely normally (that's why I think it's charging fine). Battery was tested after the first time this happened by a very reputable guy and he said it tested great. Given that, and the amp readings I believe it has a "leak". I think it is related to whatever is connected to the BATT1 fuse.

 

[Todd Z]

Sounds like that is a fuse that feeds another smaller fuse panel some where in the truck......



I use a test light, Close all the doors, remove a neg cable place it in between the cable and battery... the light will be on if there is a drain.....



then pull fuses till it goes out....



Todd Z

 

[Kevin Palmer]

Could be the diode within the alternator as well and that fuse is just the link from the alternator to the vehicle.



Remove the feed wire from the alternator and see if the reading drops. If so, then I would do so digging into the diode...

 

[P M]

Thanks. Anyone have a wiring diagram for a Gen 2? I want to find out what all is downstream of the BATT1 fuse. Probably a module in there somewhere that's not acting right.

 

[P M]

No luck with the alternator. I've tried almost every plug in that thing so far. Anyone know where the airbag module is located? I did get an airbag light. Turned the ST off and restarted and it went away. Wonder if a relay is not turning off or something.

 

[Allan Reed]

I had trouble at Christmas time on my 08 St. Battery started going dead at odd times although driven daily. Airbag light did come on also. After 3 trips to dealership then finally leaving truck there they replaced battery and have not had a problem since. If I boosted truck and took it to them battery tested okay. But when left in cold overnight they could not start it and finally admitted to a battery fault and replaced it on warranty. Bad battery causes strange things

 

[P M]

Sure sounds similar. Can't argue with that. Just odd that mine did this a few weeks ago, then was fine, and now it did it again. May swap batteries in vehicles and see what happens. However, the fact that it is drawing about .16 amps just sitting there tells me something is a miss. Should be about .005 or so (so I have read and been told). If anyone happens to take a reading on their Gen II ST I'd be curious what it is.

 

[mike goff]

airbag module should b under the front of the center console, and i think the relay is above it.

 

[scott degroot]

WHat number fuse is batt 1?. I am going to guess this is also the fuse that powers up the bcm, aka sjb. The problem with finding a draw on Ford's is that the SJB will stay awake for 45 minuites after the key is turned off and the doors are closed. During this time current draw on the battery will be excessive and will not go down to normal until the system times out. If you have the Ford scan tool you can put the SJB to sleep to check for a draw. If you don't have the scanner then you are stuck waiting the 45 minutes for the system to time out between tests to find your issue adn this gets old in a hurry. Unfortunately your best bet is to take it in in this situation.



For the record anything over .050 milliamps is an excessive draw.

 

[P M]

Old battery seemed to be loosing voltage even while sitting with the negative disconnected. Was down to 11.6V. Decided to try a new battery. When in doubt, start throwing parts at it...

 

[P M]

After digging for a root cause, and not finding one, I simply swapped the battery. So far so good. We'll see if that works long term.