Does she have a radar detector in the vehicle?
Does the Taco Bell have a motion sensor that opens the door for customers?
Rather than search for villains I would visit the vehicle in the morning at the place of employment to see if the doors are properly closed and if anything is left on.
I have see some elusive battery drains that were caused by an intermittently failing door ajar switch, in these cases the automatic headlights stay on until the doors and trunk are closed, when a door appears to be open the headlights can drain the battery in an hour or two.
Good points
But why would the door ajar switch fail intermittently at work, but not at home?
The dad said the car never had a dead battery at home, I believe
In this case it may be that a door or the liftgate isnāt being closed completely.
Okay
But why is the door or liftgate not being closed completely at work . . . but no such problem at home?
Because the daughter is late to work, and is in such a hurry, that she isnāt properly closing the door?
If so, the personās behaviour is causing the problem
GM has RAP feature on Trailblazer/Envoy platform. Automatically shuts down power after 5 minutes to eliminate lighting or accessories left on from draining battery.
Could a radar signal from a motion detector used to open doors or detect a vehicle in the drive through lane cause that RAP feature to be over-ridden? Maybe telling the vehicle that is should be getting a signal from the fob at any time?
Maybe @AgentEdās daughter should try parking where her vehicle is shielded from the motion detector, i.e. the other side of the building, or as far away as possible.
It would have to match both carrier RF and programmed channel frequencies to get a response. Not likely but fairly easy to verify. All it can do is lock/unlock doors and sound panic alarm. I still think itās more likely people are sitting in it on breaks etc and using stereo etc without running engineā¦
To drain a battery in 8 hours, seems like that would take a 2+ amp draw the whole 8 hours. So if the drain is occurring all the time the vehicle is parked there, something that takes 25 watts or so must be turned on.
I believe the retained accessory power relay is switched off when a door is opened, that is for the radio and windows. The BCM should switch off the interior lighting after a period of time, even my old cars do this.
But will the exterior lights time-out if a door is left open? I think you mentioned owning one of these, I donāt so I canāt try this. I have seen vehicles in the shop with the auto headlights on an hour after the tech went home because the hood was open (not GM). The lights will stay on on some vehicles while loading/unloading the vehicle or while checking under the hood.
It would only have to be close to the carrier frequency to keep things on. The carrier would be telling it to expect an input, which of course it never gets. That should keep it in the alert or ready status or whatever they call it.
I believe so but will verify later this morning.
Ok, so get in, close door, start engine, place in drive-
All exterior lighting is now on.
Place in park, turn off engine-
All exterior lighting still on.
Open door and exit without closing door-
All exterior and interior lighting is on.
30 seconds later (programmed setting) exterior lighting goes off.
10 minutes later all interior lamps go off.
Close door and interior lamps go on.
30 seconds later they go off.
Itās always listening and comparing. It doesnāt wake up to respond until the submodule sees a match and wakes up the rest of the controller hardware. There are usually quite a few inputs being monitored in similar fashion that produce various levels of awakening.
So even continuous bombardment without an exact match has no appreciable effect on power consumption.
Man, some annoying box overlays the posting preview box when you respond individually to multiple posts in the same thread. Suggesting i should use one reply with all my replies in itā¦
Couldnāt make it go away by selecting the x and canāt read my post because preview box is blocked by it.
Nice featureā¦
Sorry, I was abducted and taken to far away lands (actually it was the
in-laws for Thanksgiving) I am back now and have read through all of the
responses. I will say that there is a lot of thought going into this. To
follow up, the car is always parked far from the drive-thru, there is no
love interest going on with the morning crew, and everything is getting
shut properly and shutting off . It sat for five days and started right
back up tonight, in the cold, but when she went to town and parked in the
upper level of the parking garage it was dead after she returned 30 minutes
later. I am now wondering about the curbing. I noticed that it barely
clears it at work and the parking garage has similar curbing. Could it be
touching it and grounding it out somehow? I have recommended that she backs
into the space to see what happens.
Could the battery simply be going bad and it hasnāt shown up on tests? I could definitely see with an older battery starting once after a 5 day layoff in the cold, but not starting up again later. āShe went into townā Iām assuming this wasnāt a very far drive? My guess is the voltage was low, but enough to start once, it was a short drive where the alternator didnāt have much time to replete the used charge, and it wasnāt enough to be able to be started again. I think @db4690 asked about the battery being tested earlierā¦did you have it tested? Do you know how old it is?
Seems unlikely that the battery was discharged in 30 minutes, there could be a charging system problem that caused the battery to discharge while driving to the destination. Use a volt meter to measure the batteryās state of charge before driving, after driving and when the vehicle wonāt start.
It is very unlikely battery discharged in 30 minutes, I would suspect a bad contact here.
Last year I was saving my neighbor from āsometimes starts, sometime I need a jumpā situation with his Sienna minivan.
It boiled down to the oxidation between the battery post and the wire clamp: it was not really loose, but whoever was replacing his battery in AdvanceAuto (āfreeā) did not care to clean it at allā¦ you get what you pay forā¦
Anyway, we cleaned battery posts and clamps and he is a happy camper for more than a year.
The battery is right at 3 years old. I had the system checked a few weeks
ago without load and under load. Everything checked out as operating
properly. I had cleaned and tightened the clamps and terminal about a week
ago. Its about 3 miles to town. She got a jump and drove it home. I let it
set for an hour and just went out to check it. It started right up without
hesitation. I may experiment by parking it over the curb and putting the
volt meter on it.
The battery has a 5 year warranty. I may just get my prorated amount left
and put it on a new battery, if I canāt find anything else.