Flat battery after every thunderstorm

[JohnT]

Hi

Have a weird problem, the last 3 thunderstorms have resulted in a flat battery.

Tonight we had one at about 20:30 and by 21:30 ford pass app was pinging saying "Remote features disabled to preserve battery "

Have it on charge at the moment.

Previous times no DTCs other than modules complaining about low voltage.

Anyone else ever hear of this? I assume a module is waking up and draining the battery.

John

 

[BigOleFordFan]

Low voltage/battery drain can be caused by a lot of things, but I would start by looking at the battery itself, having it tested under load, as well as the terminals & cables (all the way down to the starter), to make sure they have tight, clean, corrosion-free connections...

If these things don't yield any clues, then it would be time to start checking wiring harnesses, as well as the alternator and voltage regulator/vcm....at which point it may be worth it to go see an auto-electrical specialist...

EDIT: I overlooked the thunderstorm part earlier, which would seem to indicate some water possibly getting into someplace where it shouldn't be (harnesses), thereby causing a voltage leak/short that is draining the battery....

 

[JohnT]

Just to add replaced battery first time 6 weeks ago, have washed the car several times since although that's not a great test as the car is either running during a automatic wash or started soon after with wand wash. But I was running torque pro and didn't see any super increase in amps from alternator.

But yes a bad ground is where I am leaning to and tracking down which one is going to be hard given the intermittent nature.

 

[Benztech]

I agree with water intrusion. I would start by checking codes again and go from there.

 

[BMW2FORD]

The Expeditions and F150’s are famous for water getting into the fuse / electrical junction box under the hood at the back firewall passenger side. Water from the windshield dumps right on top of it (bad design). Good to check that the lid is on tight.

 

[5280tunage]

seems to me you pay for the "full battery power" subscription in the FordPass app. 12.95/mo will unlock all 12V. J/K but seriously i just read that GM, who is using ChromeOS in their infotainment systems is now charging 12.95/mo if you want to use Google Maps, which is already baked into the Infotainment.

 

[JohnT]

Just an update had a flat battery again today but was not fully dead. Did a mV test on all the fuses you can test with terminals and nothing popped up. Borrowed a thermal camera and low and behold the 12V cigarette fuse was warm. This is marked as fuse 100, power point 5 , a 20A fuse. It's a case fuse so I don't have the means of doing a mV drop voltage test on it but still, a 12v cigarette adapter is drawing power

Aha, it's the Uniden R8 radar detector, which is set to time off after 30 minutes. (been set like this for 2 years, no issue before) And AFAIK the 12V outlets time out after 75 minutes. So I unplugged the detector, the 12v adapter felt warm in my hand and waited 20 minutes and the fuse was no longer warmer than the others. Smoking gun!!
Problem solved I think but curious me went and pulled up the wiring diagram and fuse 100 is for the luggage power point according to alldata so now I am confused




So the plan of attack is to dig out forscan and set the time out to something like 10 seconds and confirm the 12v does shut down or not.

If it is indeed the radar detector, get the hardwire kit and wire it into a switched ignition source.

If its not the time out back to square one and wait for another incident and see if anything else is warm. Full disclosure once I found what I thought was the smoking gun, I didn't do a mV test on the fuses in the passenger area because, you know, I found it or not

 

[Benztech]

Good to hear you're making progress.

 

[JohnT]

The plot thickens

Used forscan to shorten the timeout, and that works as expected with power to 12v adapter killed after 30 seconds as proven by a charger adapter with a red led attached. I can see the led lit after doors closed and alarm set, 30 seconds later the led goes out. So unless the bcm is waking up for some reason, the 12v power draw and radar detector theory is out.

Last night I got an alert about 11:30 pm on the ford app, battery saver mode enabled. No thunderstorm, no rain.

Went out and sure enough no power but interestingly the ambient light LED for the front bin where the USB ports and wireless charger are located and the rear radio console were lit up. I think the radio looked like it was back lit but was black, like when you apply power to a TV or monitor but its not got a signal? maybe? hard to tell.

No other lights, overheads doors etc were lit. The problem with these cars is as soon as you open a door lots of things come to life so diagnosing an intermittent like this is hard.

So quick review of the schematics shows that the front ambient led for the bin and the rear console get power from the BCM labelled "DEMAND LP/BATT SAVE (FET)" and gets its power from a 50A fuse 76



And that feeds power to lots of places like vanity mirrors doors etc but interestingly every other location is either a switch such as the glove box or vanity mirror lighting or a Lin controlled module i.e. it gets power but needs a network signal to turn on or feed power to the relevant light. Only the rear console and the led in the bin are directly fed power.



Still no idea why the BCM is turning that FET on and feeding power, current thoughts are radio doing an update, wiring issue/short/water or faulty BCM

So for now I have updates turned off on the radio.
Thoughts and ideas welcome, and any recommendation on a battery monitoring doodad so that I get an alert on battery voltage a bit quicker than the ford app does it, I'd like to try and catch this in the act rather than after the battery dropping to 10V

I hate intermittent faults with long time periods like this. If it did it all the time I'd be done weeks ago

Edit just posting this here for posterity and in case someone else ever hits a similar issue, if this is of no use I'll stop posting unless I find a definitive fix.

 

[5280tunage]

I think showing your troubleshooting steps like this is always super constructive for the community. I appreciate you taking the time to do tihs.