Noticed on start-up, the battery light appeared on the dashboard. However, it disappears after driving. The last time the battery was replaced in 2018, I ended up replacing it as a precaution anyways. Even with the new battery installed, I still get the battery light and it disappears after driving. Now my attention is the alternator (has been replaced once back in 2014). I don't notice any diming from the interior/exterior lighting when I turn the heater fan full blast with the radio running. Could it be the alternator?

This issue first occurred when the temperature (Celsius) dropped to single digits.

 

The battery light indicates its a voltage issue. If its occuring intermittently & you've replaced the battery its almost guaranteed to be your alternator.
I'm assuming when it was replaced in 2014 it was a 3rd-party aftermarket part?

Many autoparts stores offer free alternator testing, that is if you're able to pull it from your car.

At some point the battery light will come on permanently meaning its completely failed and your car will be running on a very short power reserve.
If this car is meant to be a reliable daily I'd recommend replacing it with a Denso Reman. from RockAuto.

 

My testing - connected Torque Pro. Visualized voltage on ECU and battery. Sudden drops in voltage were visible. When change the alternator, the issue disappeared.

 

Thank you! Yes, it was replaced with an aftermarket part. Would Bosch remanufactured be okay? There are no Denso available at Rockauto.

 

I honestly couldn't tell you as I don't have experience with Bosch. I do know for a fact that the Denso ones have the highest rebuild quality, lowest return rates.

I don't know why the Denso is not showing up for the TLs on rockauto but I found this direct link for the part that fits 04-08 TLs that is in stock.
https://www.rockauto.com/en/moreinfo...&pt=2412&jsn=1

You can verify the part # on Denso's Official Website.
https://www.densoautoparts.com/

I see that you're from Canada. Even though Rockauto is state-side they had super quick, fee-free shipping to Western Canada for me. The core return was the same.
And if I'm not mistaken its literally somehow the cheapest option even after paying USD/CAD fee. I should mention the return shipping deducted like $20CAD from my order.

Hope this helps.

 

OMG, thank you!! I have always ordered from Rockauto and with the shipping and currency conversion, Rockauto always has the cheaper price. My local auto parts store sells the Denso Remanufactured alternator for $380 CAD and Rockauto has it for $286 CAD