Does anybody else have this issue? When driving with one or both of the overhead lights on, do they dim slightly when you press the gas, and go back to full brightness if you take your foot off the gas?
It's done this ever since I bought it. Bringing it to the dealer soon, but wanted to check here too.

 

How old is it?
How old is the battery?

I have had a battery in my first Outlander start going bad. The first symptom was the heater blower fan would slow down when the head lights were turned on.

 

It is a 2013, and I think I remember seeing that the battery is new from the records - I'll double-check on that though.

 

another idea, could be the voltage regulator failing on the alternator. I once had a GrandPrix, that had the voltage regulator fail on the alternator. At idle speeds, all was normal, but when above a certain RPM, lights dim...radio cut out...engine didn't run well. I removed it and took it to a parts store for testing. It tested fine there, but they also stated that the RPMs resemble what it is at idle. I re-installed the bad alternator, and watched the voltage with a volt-meter...sure enough, the voltage dropped when it hit a certain RPM. I put a new alternator in there and it worked just fine.

 

I would check your battery cables and ground for corrosion before spending any money. If there is corrosion, your car might not be getting all the amperage it needs and would explain the drop in voltage when turning on accessories.

A bad battery wouldn't explain it unless there was an internal short(2 plates touching), but then voltage would always be low and you would have trouble starting the car.

A bad alternator or voltage regulator would explain it, but usually alternators just stop outputting at higher rpms, or die altogether. Outputting lower than normal amperage is also possible, but i haven't seen it.

I keep one of these in my toolbox, helps me keep an eye on my alternator and battery system:

 

Thank you for the input! The car is under warranty - and is going in on Tuesday for a check over to see what's going on - I wanted to be aware of what the possible causes are so I go in educated. Thanks everyone.

 

The shop cleaned the battery terminals but told me the battery and alternator tested fine - and they did in fact tell me that the dimming / light flucuation is normal - I've never had this happen in any other vehicle I've owned. It was better, but is back after a day.
Does your car's interior lights dim, when coasting, with your foot off the gas pedal, and the you press the gas, they dim a bit? Also when you engage the power windows, pressing the button down? I just want to make 100% sure I'm not just overreacting.
Does your car do this?

 

To be honest you would expect the opposite to happen as the higher the rpm the more power created by the alternator....

Do the lights just dim for the length of time your gassing or do they flicker/fluctuate if you keep at a constant high rpm?

 

We went back and talked to another guy - they insist it's normal and there's nothing to worry about - just the voltage regulator doing its job.
At this point, I'm just going to just take a step back, and if something actually breaks, I'll have it fixed under warranty.
I have the option to add an extended warranty (No, they didn't push it on me - I asked them) - 5 years, 125K miles bumper to bumper for $2,100. I think I'll go for that, so it's off of my plate. Agree?
They dim only when I'm gassing, or pushing up the power windows.
It's not a significant amount of dimming, but enough to bug me. He suggested replacing the bulbs with LEDS which use less voltage - I don't like the color of LED's though.

 

LEDs come in many different colors...

The power train warranty should last 7 years or 160k miles which I would expect to be where the problem lies if it's systemic. You can take a multi meter and measure the voltage and see if it's actually dropping and by how much.

If it really bugs you that much you can go for the warranty. I've never though of those extended warranty's as anything but a money grab for the dealer...

It's unlikely that you will have any major issues with that new car and the PT warranty will cover the big stuff if it happens.

$2,100 worth of non PT repairs seems like an unusually high number in 5 years on a nearly new car... However it's your money and your car so if you think you need it go for it.

I have a 2010 Outie that hasn't had any problems that were not covered by the PT warranty or recalls.