A strange problem started two days ago where I can't open the door from the inside on my '07 RL. Two months ago the dealer replaced the outside handle due to the keyless unlock not working so I suspect this is related but why after working fine for two months? I arranged for the dealer to service it on Tuesday but is there anything I can check before then? Fuse, relay, etc?

 

I would be surprised if the two issues were related.

I believe the door handle inside the car is a mechanical release, not electrical.

I assume you have also verified your door is unlocked when you try to open with the interior door handle / release? Be aware the RL has several mechanisms to control the door lock aside for the door lock lever by the door handle. You can also have the RL MID configured to unlock the doors when shifted into Park.

If it is not related to the electric door lock mechanisms, likey the release leaver has somehow become disconnected inside of the door.

 

The passenger door works just fine so there must be something wrong with the mechanical mechanism.