Have a Harbor Breeze fan -Model AER52BP5LKRC -
It has a 3 speed fan, lights w/ dimmer and a remote.
The fan works fine with the remote. But the light only goes on and off - it won't dim.
Is it wiring or the fan/lights?

Are you holding down the light button or the dim button? If it is actually broken it would be the remote receiver, presumably, or the remote control. Not wiring.

We replaced the receiver and the remote. There is no "dimmer" button on the remote. The description from the manufacturer says "Remote control with LCD with 3 fan speeds plus an "instant off" button and full range light dimmer". The remote only has two actual buttons- one with a picture of a light and the other with a picture of a fan, then there is a LCD screen above that. The instructions say to hold down the light button to dim the lights. So, any ideas?

You replaced the receiver and the remote, and now it's not working? Sounds like maybe the replacement(s) are defective. Can you exchange them?