This morning had a nasty surprise... never a boring day with this car.

Tried to turn on the car but the battery seems like it was dead. It wouldn't want to turn.
Lights were on and everything else seemed OK but it would not want to turn.

Pulled my wife's car around the back of it and jump started the car.
Got inside the car and I noticed that some of the vents were half opened. The car started right away, removed the cables and let it run for a while.

I've reset the vets by turning off and on the climate control but I noticed that there was no air coming out of the vents - even when I turn the knob on full blast.

Since I missed my day work now, I even went for an hour drive just to make sure the battery charges up.
Even after my drive, the blower were still not working.

I don't know if this is related with anything, but the odd thing is that I hear some sort of blower coming from the rear passenger seats (trunk area!?), but I don't feel any air from anywhere.

Any idea what might of happen and how could I fix this?
Kind of in need to fix it today if possible since the defroster is not working and I am unable to drive the car in these cold mornings .

 

Your battery is still the likely culprit. The XF is extremely sensitive to low battery voltage, having said that, you should never try and charge a battery with the alternator, that is just a great way to burn up your alternator.
The battery provides power to the car, the alternator is only supposed to keep the battery charged.
The alternator is only meant to keep your battery charged from usually no lower than a 70% charged state, lower than that and your battery needs to go on a battery charger.
The XF also monitors alternator temp by way of the ECM as part of the battery charge monitoring system, this would be another reason why your XF alt won't fully charge your battery, it will basically shut down the alternator in an over temp situation, and run off the battery-shutting down other things like the climate control in an effort to get you home. But now the vicious circle of alt trying to charge the battery, ECM shutting down the alternator for over temp at 80% battery charge because it been charging from say a 40% charge, then letting the car run off of, and subsequently run the battery back down to say 65%, and so on.
Get your battery charged, and replaced if necessary..

 

Thank you for the info!
I was not aware that the ECM will shut down the alternator once it reaches a certain charge. This could still be the result of me having the OBD ELM connected in the past. I guess it drained my battery low enough that was keeping it at the limit. And leaving the car for a day in the driveway was enough to stop the car from turning on.

Anyway, following your advise, I went outside to remove the battery from the car and charge it up.
I turned it on in order to reverse it in the driveway (so the trunk is closer to the garage door), and lo and behold, the blowers started to magically work.

I removed the battery and left it connected to the charger. Will check back on it in a couple of hours.

- - - - -

Now this makes me ask a different question... how is the charging working when you drive the car on short trips?
Unfortunately for me, currently I am limited to short trips (10 - 15 minutes of driving). And with this weather (still cold out here), and kids to carry around, I do not have much of a choice when it comes to transportation.

 

The ECM will shut down the alternator when a full charge (about 13.5v) or over temp (like +50°c over an ambient temp of 40°c) is reached, whichever occurs first. On short trips the battery just doesn't get a full charge, eventually this will reach a tipping point and you got that result to pose this thread?..lol
If you're doing short trips like that, I'd keep the car on a battery tender most nights, Sears use to sell a nice one for about $30, that I've used 2 versions of over the last 20 years. I'd also unplug the elm, if your ECM is seeing negotiations going on with the elm, it may not be letting all queried systems shut down, yep draining the battery.

 

Thanks again!
I stopped using the ELM unit since I realized I had issues with power drainage (had a separate thread about it here). But I guess the battery never had a chance to charge up properly.

I will try and see if I can find a way to have the battery connected to a charging unit over night - unfortunately the XF sits outside since there is not enough room in the garage at this time.
I will be selling my track car sometime this spring and until then, that one sits in the garage.

 

DO NOT LEAVE YOUR BATTERY ON THE CHARGER OVERNIGHT unless it automatically shuts down when the battery has a full charge, if it doesn't ! IT WILL KILL IT.
Battery tenders compensate to keep the battery at optimum charge.

 

Yep - no worries!

I plugged it to the same charger that I am using to keep my track car battery charged over the Winter.
It WILL shut down when the battery is fully charged and then once it drops under a certain charge it will start charging it again.

 

As an update on this, for whoever might be interested, it took about 14 hours for the battery to fully charge... I guess that sucker was way under 50%.

Everything works as it should for now - I'll keep my eyes on it and hopefully this was due to the issues that I had with fans starting by them-self during rainy days (here) and me leaving the LEM unit plugged all the time.

 

14hrs? Sounds like you deep cycled it Probably time for a new one, but good luck.

 

Could be... it did took a long time.
I'll keep my eyes on it. The good thing is basically a new battery and there is a 2 year warranty on it so I could replace it if anything - I got it in January.