Q: There is a rattling sound when you turn the A/C on and you put the car in gear. Does not usually rattle if car is not in gear.

If the rattling only occurs when the A/C is on, you can conclude that the rattle is coming from the A/C system. If the rattle occurs without the A/C on, then you will need to dig deeper. You have clearly stated that the rattle occurs when the A/C is on, so I will address that as so.

When you put a car into gear, you add load to the motor that is felt from the accessory belts all the way to the wheels. Of course you feel this in the steering wheel and in your seat when you put it in gear. I suspect you have a serpentine (drive) belt tensioner problem. Tensioner’s manage all the load that occurs from the accessories mounted on the front of your motor. The A/C is unique among these accessories. A/C systems have other issues that can creates rattles, but they are much less common and difficult to explain in this forum.

In addition to the A/C system, you could have an exhaust shield that comes loose. The added load placed on the motor from the A/C system may be just enough to create such a rattle. There could be a loose pipe or hose that is made to rattle more with the added load of the A/C.

Your car is fairly new and I would not expect something like this from a newer Honda. I have to wonder if something such as an accident or off roading experience may have led up to this. If anything like that has occurred, I would suspect this is a result of it. One other possibility to note, there are reports of some CR-V’s having timing chain rattles. But they don’t seem to accompany the A/C being on. So hopefully this isn’t your issue, because it is a much bigger repair.

If you are still unable to figure this out, a certified technician from YourMechanic can come to your car’s location to inspect the noise and make proper repairs.