'Parasitic Drain' casuing start issues...

Does your battery have fill holes? I mean, maybe the electrolyte level is really low. Does not matter though. If the battery is allowed to discharge, it may be impossible to charge it to 100%. For them not to even look at the condition of the battery is nojoy. They mentioned parasitic drain, but probably never put an ammeter on it to test (speculating). Go back, but with some knowledge. It costs NADA to have your battery and alternator tested at these stores. If you feel so inclined, buy some windshield wiper fluid or something else from them...

 

I stand corrected! You can operate the homelink when the truck is completely off. Regardless, the Dongar connector won't power the USB connection unless the truck is running or ACC is on.

I'm also not clear on what you mean with starting issues. Does the starter turn slowly, or does it seem like the starter requires quite a few cycles before the engine turns over? A handful of times I've turned the key to start the truck and released before it's actually started. I've found from time to time the starter needs to spin a bit longer than what I'm used to before the engine fires up. I've noticed this on a hot and cold engine.

 

my issue may be different than OP, but what you describe in paragraph two is what I experience.

 

I use the same adapter. The mirror power is keyed. Your camera shuts off when the truck does. That isn't the problem.
I'm guessing you have a bad battery.

I have a 2018 VW Atlas that had trouble starting within the first few months. Once i was in a drive thru line and the auto-start turned the engine off then it wouldn't start again. That was embarrassing. The dealership tested the battery, confirmed it was bad, and replaced it. No issues since.

 

Well, just to be clear, the mirror does receive both, ignition and battery power. Not sure why that's the case.

The aftermarket harness, on the other hand, I imagine that is ignition only?

 

Are you saying your mirror is on all the time? The compass and sensor do not turn on until the accessory or engine does.

 

There is still a battery wire that feeds to the connector. If you have a mirror with garage door buttons, they will work with the engine off. Take a look at the drawing I posted on the first page and you'll see there are 2 sources of power to the mirror, one being ignition sourced and the other from the battery.

 

Seems like a bad battery to me.

 

I have a novel idea....DO A DRAW TEST. Get a cheap multi-meter, and do a one-minute test. Don't know how...here:
https://www.youtube.com/results?search_query=parasitic+draw+test+with+multimeter

I set my meter to milli-amps, and hold one test connection on a battery post....with the other on the battery cable...and slide the cable off. Take a reading. Or....just disconnect the battery (one terminal only) and take a reading across the connection. Be aware that the truck will "wake up" for a few seconds and then go back to sleep mode. Take a reading. Be sure all doors are closed when doing the test. Stop guessing and find out.

 

I like this one:

https://www.youtube.com/watch?v=KF1gijj03_0