Help with parasitic draw?

Status
Not open for further replies.
Joined
Apr 17, 2012
Messages
3,551
Location
West Michigan
Short version is that my 2011 F150 is killing batteries. Key off draw goes down the truck 40ma after about 10min and stays that way for a long while. I have no ammeter data logging capability. New battery didn't fix the issue, died after about two weeks. Like I said I'm showing 40ma after 10min.

Any suggestions for troubleshooting or common issues? I hate to take it in just to have somebody else watch their data logs overnight. Especially if it turns out to be intermittent and nothing is found.
 
Originally Posted by Quattro Pete
Do you have a web cam? Point it at your DMM and record video over night to see if current goes up. 40 mA is pretty normal.


I think most modern cars say below 20 mA is normal. 40mA will drain the battery pretty good over a two week period.
 
well at 40ma drain.. 1000 hours or 41 days would be 40ah.. battery should be around 100ah so

theoretically 40mah drain would take 3 months to kill it.
 
Originally Posted by ZeeOSix
Originally Posted by Quattro Pete
Do you have a web cam? Point it at your DMM and record video over night to see if current goes up. 40 mA is pretty normal.


I think most modern cars say below 20 mA is normal. 40mA will drain the battery pretty good over a two week period.

On newer cars, even 50-85 mA is still considered normal.
 
Originally Posted by wymi516
https://www.youtube.com/watch?v=acdNBBdJWF8



Yes, I have seen that one. I'm not going to poop away a possibly perfectly good alternator on guess work though. Especially with how much these cost now a days. The webcam is a pretty good idea but I wonder if anybody knows of maybe some type of USB dongle that would allow me to watch the draw? I guess I *could* run FORScan but its showing a 0.00 amp draw at key off which isn't accurate.
 
Originally Posted by Rand
well at 40ma drain.. 1000 hours or 41 days would be 40ah.. battery should be around 100ah so

theoretically 40mah drain would take 3 months to kill it.


What battery has 100 AH rating? My battery has a Reserve Capacity (RC) of 95 minutes to hit 10.5v (100% discharged) at a 25 amp draw, which calculates out to ~40 AH.

40 mA draw would take 1000 hrs, but a battery might be unable to start an engine when 50% discharged, which would take ~500 hrs = 20 days. So 2 weeks at 40 mA might take the battery down to ~60% charged.
 
hook up your multimeter and start pulling fuses. Disconnect the alternator as well. Start tracing. I had a decent draw on my Tb and took less than an hour to figure out what the problem was. Cost me 40$ to buy a fancy multimeter.
 
Does this have the door keypad that turns on some lights? I have seen these pads go flaky, I did one with normal parasitic draw but every few weeks sitting the battery would be dead. Luckily I parked it outside and it rained, the next night I saw it lit up with the running board lights on.
40mA is well within normal range, over 100mA you possibly have an issue. When the keypad malfunctions it draws over 2A depending on the amount of lights on.
 
Originally Posted by buck91
Short version is that my 2011 F150 is killing batteries. Key off draw goes down the truck 40ma after about 10min and stays that way for a long while. I have no ammeter data logging capability. New battery didn't fix the issue, died after about two weeks. Like I said I'm showing 40ma after 10min.

Any suggestions for troubleshooting or common issues? I hate to take it in just to have somebody else watch their data logs overnight. Especially if it turns out to be intermittent and nothing is found.


Was that two weeks of sitting without being used, or was that two weeks with use about every day?
 
You can disconnect the alternator's wires for one night and see if you wake-up to a dead battery that would rule out the diodes in the alternator. If it's not that then yank all the fuses and put one new one back per night until you find the circuit. PITA but you will find it that way. I would start with the ECM first if you get to that point. Don't forget any fuses under the hood as well.
 
Last edited:
My 2009 F150 has a similar drain. It's had it since new. And will kill a battery in a few weeks. I have to drive it every week.
 
I drive it 2-7 days a week so that shouldn't be the issue. I'm tempted to either take it in or try rebuilding the alternator but either way I could just be tossing good money away.
 
Do you have any aftermarket radio equipment? I had a satellite radio/iPhone converter wired in that never fully went to sleep, so it was draining the battery every couple of days. It was wired per their directions but something was causing a section of it to continually drawing current.
 
Originally Posted by SkipsterPA
Do you have any aftermarket radio equipment? I had a satellite radio/iPhone converter wired in that never fully went to sleep, so it was draining the battery every couple of days. It was wired per their directions but something was causing a section of it to continually drawing current.



Yes but its not new to the vehicle at all. Its an Alpine headunit that I had in my old F250 and has been in this truck for 1-2 years now without prior issue.
 
We had a similar problem on a GM TrailBlazer. I turned out to be the OnStar system sucking current and it had a separate fuse. Since we didn't use it, we pulled the fuse and bypassed the digital data system.
 
Originally Posted by buck91
I drive it 2-7 days a week so that shouldn't be the issue. I'm tempted to either take it in or try rebuilding the alternator but either way I could just be tossing good money away.


No, it's easy to see if it's the diodes and you don't have to just guess. Do like StevieC said, or put the meter in AC voltage mode and look for ac voltage across the battery when running.
 
Status
Not open for further replies.
Back
Top