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Looking at a good friend’s 2000 F250 V10. Battery drains after 2-3 days so I show up and find a .34 amp draw. Shut the glove box door and it’s down to .10 amps. Pull fuse 15 in the interior fuse box (stop lamp switch, GEM, PCM, ABS, PCM keep alive, a lot on this 5A fuse) and draw is down to acceptable levels.
Two questions; Would that .10 amp draw gone to 0 if I waited a few more minutes? Are there any common faults associated with the circuit(s) I isolated that would cause a .10 amp draw?
I’ve got access to wiring diagrams but they’re just confusing me. Any ideas?
Thanks.
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I wouldn’t be too worried about 100milliamps. With all the modules on that truck it would be normal. You’ll never see a 0 draw unless its on a Model T. Even a clock or radio has a keep alive memory and will need to have some draw to keep working. General rule is go after any draw over 500 milliamps.
Have you load tested the battery to be sure it is confirmed good? Even if the draw was a separate issue it could’ve done some damage to the battery if it was drawn down real low a few times. When I go after anything electrical I always start with a confirmed good battery. That V10 needs all the amps it can get to start up cold, and a battery that is marginal will fail to deliver. Even if it is a newer battery I would still test it. I’ve gotten batteries that were defective off the shelf before. One guy who taught me some driveability used to like to say new doesn’t mean good, just different. Its a good thing to remember to keep from overlooking something.
Didn’t test the battery. He reports that it’s new but, like you said, it may mean nothing.
The guy’s truck is around 30 minutes away so I won’t make another trip out there unless he’s stuck. I already got the draw down from .34 to .10 so maybe that will keep him going. Didn’t even charge the guy (battery or owner 😉
I have to disagree about 500mA being the point of chasing a draw. The industry standard I know to be the maximum acceptable amount is about 85mA, or 0.085 Amps. That would apply to a major luxury mobile like Mercedes/BMW/Caddilac/Etc super high line luxury models with 50+ control modules and a battery 2-3 times the size of a Honda battery (usually under a rear seat or in the trunk).
On the new Mitsubishis I deal with that are running 8-12 physically separate computers, over 30mA is considered a problem. The general rule I apply to cars I don’t know well is 50mA and under is to be disregarded, and 50 to 100 is to be suspicious of. 500mA is quite a severe draw, bigger than I’ve ever diagnosed. Most daily drivers with average 500CCA +/- batteries won’t have trouble with a draw until it’s over 120mA, but a new battery can conceal that amount for awhile until the nightly discharging starts wearing it down.
Quick story of a memorable draw diagnosis was on a 2004 Diamante VR-X, the flagship luxury car of the time with all the doo-dads. It had a 170mA draw that I chased to being the Front ECU (a body control module), using standard draw diag procedure. You could assume the module is just faulty and needs to be replaced, but you have to ask why. Turns out the lock cylinder in the driver’s door handle has a sensor that clip to the back of it so the ECU can see you turn the lock cylinder and unlock the other doors. Old plastic broke and the sensor fell off in a turned position, so the Front ECU always thought there was a key holding the lock in a turned position, so it never powered off.
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