Battery Keeps Draining...

Hey to all on this Taco Sunday!!

2016 TT TRD Sport - Woke up the other day and truck was dead...no power. Put another spare battery in and went and bought a new battery; had alternator & starter checked - no problems. Thought all was good, but next day...dead. Had charged the spare battery overnight and swapped it.

Multimeter test showed 12.63V for the battery. Performed the parasitic draw test; disconnected the black cable, flipped to amps and it showed no draw on it, 0.00, which concerned me because I would think it would show @ least 0.1 or 0.2 (yes, tested leads to ensure they were working). I also did allow 30+ minutes to pass so it would go into "sleep mode."

The really weird part of this is that when the multimeter, in volts, is placed on the battery and I touch the positive post (cable on it) and the negative post (cable off it), it shows 12.63V, but when I do the same thing, but put the negative cable on the post, it drops to 10.22V (hope that makes sense).

Something is clearly draining the power away...just clueless as to what.

One thing that may shine some light on why this is happening is that I think the sunroof drain is clogged. I have found water on the driver's side pooled in the WeatherTech a few times over the last few months as we've had a really rainy fall/winter. Also the carpet/padding were very damp. I'm sure that water has gotten into the driver's side cab and probably onto the electrical components where the internal fuse box is.

Thoughts/ideas??

Thank you very much in advance!!

 

Hey there, for now I’d start by fixing the sun roof and drying things out, grab a couple a/c dryer desiccants from online and throw them inside to cab, see what that does.

 

typical parasitic draw should be less than 50mA ie .050A. is your meter on a sensitive enough scale?
and were you measuring in series from disconnected post to disconnected cable...sounds like you were but just in case.
also check fuse on meter. easy to blow them if on wrong scale and overload it (prob not this time but maybe in the past...i've done it...pita).
edit: or maybe this time...check fuse in meter and start at highest current scale and descend as necessary. the voltage drop you saw may indicate a massive draw.

 

Thanks PDX...I had it on the 10 amps setting and thought that was sensitive enough, and yes, was measuring from post to disconnected cable. Good point about the fuses...we looked at all of them and they all looked good. Just baffled by all this. Even my son, who's an electrician, said that that makes no sense.

Thanks again!!

 

your wording sounds like you looked at "all of them" fuses meaning truck fuses?? i meant in meter. should only be one or two.
10Amp may not be sensitive enough to pick up 50mA but is where you should start (i edited while you were responding i think)
edit: i think i'd prove the meter amps by getting a real reading on some other source (output end of a wall wart in use charging a phone etc).
edit 2: maybe phone not the best example, you'd need to make a frob or cut wires - maybe something simpler DC.