The Infamous Battery Drain Issue -- My steps so far -- need suggestions

1950StangJump$ · Aug 1, 2018

So, it amazes me that there are 12 years of threads on this topic and no definitive answer.

I finally got my car about where I want it, so circling around to some "minor" deals I had put off. Its a weekend driver -- I put maybe 4k miles per year on it. But, if I go more than 4-5 days without leaving it on a battery tender, it won't start. Very annoying.

The facts and my actions so far:

I have a 2008 GT with a Kenne Bell. Originally a Shaker 500, but the head unit is now aftermarket.

It has a relatively new (and high quality) battery that tests good.

It has a new alternator -- the previous owner alleges it was one of the "high output" types. If so, I understand that they charge better at higher RPMs but worse at idle. Still, it shouldn't be the problem, and my Aeroforce gauge says the car is charging fine.

When I put a voltmeter to the car battery after I had given it time to sleep, it showed a draw fluctuating between 70 and 100 milliamps. Roughly two or three times the acceptable draw, from my reading.

Surprisingly, it is not the Shaker 500 amp. But, when I pulled fuse #67 at the Power Distribution Box, the draw dropped to 20-30 milliamps (acceptable)

When I put the fuse back in at first, it would jump right back up to the 70-100. I thought I was on to something. As I removed the fuse and put it back in a few times trying to diagnose, the draw eventually dropped to 40 milliamps with the fuse in and stayed there. I don't know why the change, but 40 should be okay. It still dropped to 20-30 when I pulled the fuse.

#67 says it is the #4 power to the SJB. I then pulled a bunch of the fuses in the SJB, but not all, before I got frustrated and quit. I was sure to pull the passive alarm fuse, the motion sensor fuse, the radio, etc. No change.

Has anyone been successful in figuring this out?

redfirepearlgt · Aug 1, 2018

Fuse 67 feeds the smart junction box. It feeds four fuses on a bus in the SJB. First pull the passenger side kick panel and inspect in there for water intrusion to the Smart Junction Box (common to happen). IF water evidence is found pull connectors and use a hair dryer on warm or cool to dry out the connectors and SJB as best as possible if you find evidence of moisture. Then search for the fix that resolves the water finding its way into this area of the vehicle when the car is washed or sits out in a heavy rain.Afterward recheck your current drain as you have been doing. If it is still present continue on.

Plug F67 back in and monitor current drain. On the SJB pull F9, F10, F11, F8 one at a time and see which one causes the current to drop back down to 20mA. If it does not Disconnect C2280H connector and see if that drops the current. If it does the power bus that F67 feeds in the SJB also feeds internal power for the board functions of the SJB which means your SJB may need to be replaced.

F 9 feeds the climate control module
F10 feeds the overhead console
F11 is not used but should be pulled anyway as part of the TS process
F 8 feeds the instrument cluster and Data link connector (where your diagnostic or programmer would plug in).

Should the problem be related to one of these Fused circuits and not the SJB follow up with your findings.

I take the time to help here for the experience of helping others and a continued learning process of the internal electrical circuits for these cars. It's my time I spend so I ask you be considerate in following up with what you do find. My future assistance as it is hinges on how well a person follows through with direction and then follows up with his/her findings.

RocketcarX · Aug 1, 2018

In addition to what RedfireprealGT says the aftermarket 6g alternators are trash, and unless you test the system specially for an AC ripple it might always look good from the gauges.
I would do the 09-10 Denso alternator swap myself

1950StangJump$ · Aug 2, 2018

Thanks, guys. Redfire, that is great info, and I will definitely follow up. The interesting thing to me . . . with #67 in, it started out as a 70-100 mA draw, then dropped to 40 and stayed there after I played with it for a while.

Whether at 70-100 or 40, when I pulled the fuse, it always dropped to 20-30. Assuming 70-100 is unacceptable, and 40 is acceptable, it makes me wonder if the SJB is intermittently leaving something on . . . and it is the SJB that needs changed out. Note, this car does NOT get driven in the rain, so water damage in the area is not likely.

Rocket -- I know the alternator is new, and it certainly looks new, but I'm frankly not positive what was put in it. I can see no obvious part numbers or brand name on it. The connector looks like the original, i.e. a different one was not spliced in. I just know that list of modifications said "upgraded alternator." It could be the 09-10 Denso, for all I know.

1950StangJump$ · Aug 2, 2018

Also, if I leave the passenger door open, will the car eventually still go to sleep? It would make playing with the SJB so much easier with the door open. Just flipping the door latch did NOT make the interior light go out, so I gave up there . . . but I didn't try simply leaving the door open during the 30 minute window when I'm waiting for the car to take a nap.

Juice · Aug 2, 2018

A 100 mA draw will not kill a good battery in 5 days. So, you either have a larger intermittent draw, a weak charging system, or a weak/dying battery.

I would charge the battery FULLY, and verify charge by voltage. 12.6 V or better without any load on it. Now leave the battery disconnected and see if it still dies in a few days. It should maintain 12.6 V or very close to it.

Wes06 · Aug 2, 2018

You will want to use a screw driver to close the latch on the door .that is where the sensor for open/shut is .Instead of a plunger like many other setups

1950StangJump$ · Aug 2, 2018

Hmmmm. Juice, the battery tested good a couple months back. I could try again.

I wonder about this combo: If a 100 mA draw drains the battery somewhat (but allows the car to start), and then I drive a short distance not letting it get a great recharge, perhaps with an alternator known to charge well when you work the car hard but not when putzing around, and then park it for 5 days . . . that perhaps that combo could be enough to cause the battery to die. It's not completely dead at 5 days, just enough to not let the car start.

Wes, when I flipped the latch, the interior light stayed on. It always stays on for a while, but it continued to stay on with the latch flipped. Are we sure the latch doesn't have to ground against the post (like when the door is shut) in order to make the car believe the door is closed?

redfirepearlgt · Aug 2, 2018

I suggest you stay focused on one thing at a time. If all checks out with the SJB, and you are down to swapping that (since this is the rabbit hole you chose on the current drain issue you are seeing which makes sense) then complete that before moving on to Rocket's suspect of the charging system which I agree should be checked next. Stay focused on that task before moving on. There is nothing worse in a troubleshooting process than jumping around before eliminating a distractor in the process of elimination and isolation.

BTW - I assume you wash the car though it never sees the rain. So therefore it gets wet and the water can build up and find its way into the SJB area when the problem that is common to causing this occurs. BUT THAT IS AGAIN A DIFFERENT ISSUE THAT CAN BE ADDRESSED IF WATER INTRUSION IS FOUND. I wanted you to read this I am not yelling.

To quote Red leader in Star Wars - STAY ON TARGET....STAY ON TARGET.

1950StangJump$ · Aug 2, 2018

redfirepearlgt said:
I suggest you stay focused on one thing at a time. If all checks out with the SJB, and you are down to swapping that (since this is the rabbit hole you chose on the current drain issue you are seeing which makes sense) then complete that before moving on to Rocket's suspect of the charging system which I agree should be checked next. Stay focused on that task before moving on. There is nothing worse in a troubleshooting process than jumping around before eliminating a distractor in the process of elimination and isolation.

BTW - I assume you wash the car though it never sees the rain. So therefore it gets wet and the water can build up and find its way into the SJB area when the problem that is common to causing this occurs. BUT THAT IS AGAIN A DIFFERENT ISSUE THAT CAN BE ADDRESSED IF WATER INTRUSION IS FOUND. I wanted you to read this I am not yelling.

To quote Red leader in Star Wars - STAY ON TARGET....STAY ON TARGET.

Okay, fair enough.

As I pull off the cover to the kick panel and look at the fuses, if it is not wet now, how would evidence of prior water manifest itself?

s8v4o · Aug 2, 2018

How old is the battery?

1950StangJump$ · Aug 2, 2018

s8v4o said:
How old is the battery?

Maybe 1 year and less than 4k miles. It is a Motorcraft Gold. Tested good about a month ago.

redfirepearlgt · Aug 2, 2018

You may see staining or smell a musty smell in the area. Light rust on surrounding maouting hardware, etc. You can also remove the mounting hardware the holds the SJB in place and use a mirror and light to look behind it to see if there has been moisture trapped or still trapped behind it. White rings, from mineral deposits in the water left after it has dried are typical signs of water intrusion on most things. If there is no evidence that is overly obvious. Begin pulling the fuses I listed that are on the bus that F67 feeds. I know we are looking at 100 mA of current which is not a lot, but would drain a 45aH battery from full charge to dead flat 0 in 18.75 days (45aH/0.100A*24hrs = days to drain at 100mA draw). The ability for the battery to turn the engine over (avg current needed on a V8 is 125 amps+ based on warm oil and ambient temp. Double that in the winter) would be depleted in even less time.

If there is nothing significant found in doing this we can then refocus on the charging system that everyone keeps harping about. I would have begun with it first, but since you had already gone this route it was best to finish it before moving on.

1950StangJump$ · Aug 2, 2018

I got to be thinking . . . I drove the car Tuesday morning around town running errands. At mid-morning, I loaded a new tune into it. Keep in mind, I have the VMP dual fan heat exchanger, so two fans and the intercooler pump were operating while the car was in 'run' and I was loading the tune. When done, I started the car, then remembered I hadn't put the radiator cooling fan temps where I wanted, so I immediately shut it down and did a tune load again with the right temps. The 2nd tune loaded but, by the time I was done, the battery had only enough juice to turn the car over a few times -- and it went too dead before starting. I then had to jump start it.

Point here, the car had been run earlier in the day, but didn't have enough juice to do a 3 minute tune load with fans/pump running, a quick start and shutdown, and then another tune load with fans/pump.

Also, I just tested the draw again. Not sure what hadn't kicked off last night when it first showed the 70-100 mA draw, but it was back down to 40 today after the car went to sleep (like it went to eventually last night). As a matter of a fact, I put a 2nd voltmeter on it, and that one showed only 30 mA draw.

So, while I had assumed I had a draw issue, wouldn't this point to battery or alternator now? When I start the car cold and it idles fast, it shows 13.8-13.9 volts on my Aeroforce gauge. When it idles down after a few seconds, it settles in at 14.0-14.1 volts. Once warm, it settled at 13.6 volts, and it dropped to 13.1-13.2 when I cranked the a/c. Again, HE fans and intercooler pump going strong.

The car has not been washed in a couple weeks. While I have hit the occasional puddle, it has not been in a rain. So, I can't see how any water would have gotten in the SJB area causing this . . . so, I didn't even check that.

Juice · Aug 2, 2018

1950StangJump$ said:
I got to be thinking . . . I drove the car Tuesday morning around town running errands. At mid-morning, I loaded a new tune into it. Keep in mind, I have the VMP dual fan heat exchanger, so two fans and the intercooler pump were operating while the car was in 'run' and I was loading the tune. When done, I started the car, then remembered I hadn't put the radiator cooling fan temps where I wanted, so I immediately shut it down and did a tune load again with the right temps. The 2nd tune loaded but, by the time I was done, the battery had only enough juice to turn the car over a few times -- and it went too dead before starting. I then had to jump start it.

Point here, the car had been run earlier in the day, but didn't have enough juice to do a 3 minute tune load with fans/pump running, a quick start and shutdown, and then another tune load with fans/pump.

Also, I just tested the draw again. Not sure what hadn't kicked off last night when it first showed the 70-100 mA draw, but it was back down to 40 today after the car went to sleep (like it went to eventually last night). As a matter of a fact, I put a 2nd voltmeter on it, and that one showed only 30 mA draw.

So, while I had assumed I had a draw issue, wouldn't this point to battery or alternator now? When I start the car cold and it idles fast, it shows 13.8-13.9 volts on my Aeroforce gauge. When it idles down after a few seconds, it settles in at 14.0-14.1 volts. Once warm, it settled at 13.6 volts, and it dropped to 13.1-13.2 when I cranked the a/c. Again, HE fans and intercooler pump going strong.

The car has not been washed in a couple weeks. While I have hit the occasional puddle, it has not been in a rain. So, I can't see how any water would have gotten in the SJB area causing this . . . so, I didn't even check that.

The above description is telling me one of two things: Your battery is NOT FULLY charged, OR, the battery has lost capacity and IS FAILING.

1950StangJump$ · Aug 2, 2018

Juice said:
The above description is telling me one of two things: Your battery is NOT FULLY charged, OR, the battery has lost capacity and IS FAILING.

Agreed. When cruising around, I'm seeing 13.5ish volts on the gauge with the fans going. Drops to 13.2ish if I crank the A/C. Is that low?

Is it as Rocketcar says -- while that might be okay on the gauge, it could still be not charging the battery correctly?

redfirepearlgt · Aug 2, 2018

I have a VMP triple pass myself and NEVER reflash the car without pulling the fuses on the HE fans before hand. The fans and the I.C. recirculation pump are tied in with them ONLY draw about 33 amps of current as I recall they told me when I asked.

Your initial post indicated you had already done this since you had already mentioned it as indication it was fine, had proper DC output of 13.8-14.4 while regulating and have minimal AC ripple.

It has a new alternator -- the previous owner alleges it was one of the "high output" types. If so, I understand that they charge better at higher RPMs but worse at idle. Still, it shouldn't be the problem, and my Aeroforce gauge says the car is charging fine.

You can't seem to stay focused.

Terminado.

1950StangJump$ · Aug 2, 2018

Back it down, tough guy. Now YOU need to stay focused instead off getting your knickers bunched up. . . pulling the fan fuses is irrelevant to whether the car is holding PROPER charge. The fans alone would not have been enough to drain the battery if everything else was fine. And you have apparently not been around the block enough to know that you cant comment on another man's "intent." My intent was always to leverage the best, most reasonable courses of action to fix the issue.

I started this thread knowing: The previous owner had done the alternator, so I viewed it as an unlikely culprit. I had the battery tested, though it was relatively new also. I also new that 4-5 days without running meant my battery was dead. And there was a ton of info on batteries being sucked dry on these cars.

So I started looking for the parasite . while 30-50mA aint perfect, it wouldnt be killing my battery. The problem is obviously a bad battery or a shitty alternator.

Dino Dino Bambino · Aug 3, 2018

1950StangJump$ said:
The problem is obviously a bad battery or a shitty alternator.

If the voltage across the battery is at least 1.5v higher with the engine idling (no electrical loads) than when the engine's off, the alternator is providing adequate charge.
A difference of 1.0-1.5v would be borderline, and less than 1.0v indicates a weak alternator.

1950StangJump$ · Aug 3, 2018

Dino Dino Bambino said:
If the voltage across the battery is at least 1.5v higher with the engine idling (no electrical loads) than when the engine's off, the alternator is providing adequate charge.
A difference of 1.0-1.5v would be borderline, and less than 1.0v indicates a weak alternator.

Assuming that the battery should be at 12.6 when the car isn't running, and assuming my Aeroforce gauge is accurate, I guess that would put me at borderline. Idling when warm, I'm seeing 13.6 with no A/C running. Drops to 13.1-13.2 and stays there when I turn on the A/C. Not sure how much the HE fans running affect that. What I am not sure about . . . is that low enough to cause the occasional dying battery issues that I am experiencing?

The Infamous Battery Drain Issue -- My steps so far -- need suggestions

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