2008 nissan sentra shifts perfectly unless headlights are on. I can flip headlights on while driving and automatically feel trans upshift and become extremely weak. I can flip them back off and trans starts working properly again. Alternator is charging 14.3 with lights off wnd 14.2 with lights on. Everything on the car seems to be factory. Any clue? Thanks

Hey Adam, welcome to NICO Club!

That's a bit weird. Maybe a bad ground? I wonder if you have a check engine light when this happens.

You can check your battery for voltage (should be 12.2 when car is off, near 14.4 when on as you've already tested) and amps. The amps test might give a clue, but I guess the car starts fine on a cold morning, so those may be fine also. You could still test and see the dip in amps when turning on the headlights.

I moved this topic to the Sentra forum.

Not sure if you managed to fix your issue by now but I recently had a similar issue with my '13 Sentra.
Had the rear taillights replaced after an accident and the car drove fine until I tried to use my left turn signal. When the turn signal was on the CVT wouldn't shift and the car would damn near stall out. In addition, on my dashboard where the LED shows what gear the car is in, in every gear ut reverse the gear symbol would blink in sequence with the turn signal. Almost wrecked it four times in an hour.
When I took it back to the shop, they played switcheroo with the wiring housings and we realized that the wiring had been wired incorrectly with the new part. The shop suspected that the incorrect wiring wasn't grounding something and that it was also wired through the CVT.
So, I'd guess that you have a bad ground or something that's wired incorrectly.
Hope this helps!

That kind of stuff to be expected now with 5 miles of wire in the cars and the wiring connects everything to everything else.

I don't know if this will help but I recently discovered the ground strap under the battery was completely severed. It is on the driver's side and goes from the subframe to the trans on my 07. I have replaced it with an autozone cable and crimp connectors. It fixed a misfire problem. Check and/or replace all engine grounds... the top one on the passenger side looked fine too, but upon closer inspection the wire was all corroded inside. I replaced this one too for good measure.