Where's the ground? Losing battery volts.

[bamaboy473]

Our 2002 7.3 Excursion is a month old to us and when it sits for over 3 days, it's a bear to start; sluggish turnover.
Last week I started comparing this truck to our other Excursion with a voltmeter and found that the batteries are fine, and they hold a charge when disconnected. connect them back up and the volts start to drop like rocks.

First question would be to find the ground strap and make sure everything is tight. With my bad back, I'd rather have an idea of how to get to it the first time, so any help locating it would be appreciated.

Second is that this new truck had a lot of extra electronics added to it. How can I test to learn whether the volts are leaking through an appliance instead of from a bad ground?

[Banshee34]

Bumping this up for ya!

[NCHornet]

Something is drawing the batteries down, I doubt it is a bad ground, and I am sure the EX is different from the Superduty so the easiest way is to just follow the ground cable, shouldn't go far!!
But to test the system, start with fully charged batteries. Take a volt reading at the battery, and then start removing fuses one at a time, when you see the volts jump up, you know the drain is on that circuit, then it's time to start looking at what's on the circuit. I would start with any aftermarket stuff that has been added, like stereo, alarm, etc... My buddy bought a truck and the PO wired the stereo to be on all the time, but never told my buddy who hardly listens to the radio, it just had it turned way down, but itwas still drawing and leaving him with dead batteries. Good Luck

NCH

[symbols]

You have a case of phantom draw. You don't look for voltage though, you look for amperage. A normal vehicle will pull less than 1 amp when turned off. Anything higher than that and you will have the problems described.

What you need to do is set your DVOM to amp. The next part is tricky without a special tool but you can still do it. Put one probe on the neg cable and one probe on the neg bat post itself. Now take the negative cable off without losing contact with the cable or the bat. If you do it any other way, you can "wake up" components and it will give you a false reading. Once you've done that you can start pulling fuses. Like was said before, I would start with aftermarket accessories first as they are usually the culprit. Hope this helps.

[bamaboy473]

You guys have given me a plan for starting the tests. I'll report in tomorrow with readings and results.
Thanks for the help!

[forddieseldoctor]

50 milliamps max is the spec from ford after like 45 minutes of sitting and letting all the modules go to sleep

[SCUFFY828]

Originally Posted by forddieseldoctor

after like 45 minutes of sitting and letting all the modules go to sleep

this is the key to finding a draw in these vehicle , you have to wait until the accessory delay relay shuts off or you are wasting your time

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Last edited by SCUFFY828 : 10-09-2008 at 07:19 PM.

[bamaboy473]

OK, so I'll drive it a couple miles in the morning, then eat breakfast and wait an hour before starting the fuse and amp tests. We're good to go, we can do that.

[tubular031]

Something you might want to consider, add a few ground wires. I do this on every thing I add things to. you have this super high power amp on fat wire pulling lots of power right? well you string a wire to the + on the bat and then run the - to something metal. well take a look at how that - off the bat is connected. On most things its 1 little 10 gauge wire. so What I do is add a few wires from the - on the bat to the frame in a few locations. This will allow the frame to handle more power draw. on my truck I added 2 on each side to existing bolts. Just slip the spade connector under a bolt and connect it to the - on the battery .

ALso make sure that you put a fuse on all + wires you add and make sure that fuse is as close to the battery as you can put it (like a couple inches not feet!)

[bamaboy473]

I ran the truck, let it sit for an hour and the volts read 12.48. Then I got into the fuse box and started pulling fuses (darn thing has 50+) When I got to 35 the volts spiked and I thought I had found something, but it was just the door and running board lights.

Nothing found on the regular fuses and nothing looked added on. There's a bunch of wiring around there, though, and the big amp under the rear seat is hot all the time. Today I'm going to check the ground for that thing, disconnect the inverter and add a couple ground straps like Tubular suggested.