power/heated mirrors not working

My '99 Cherokee Sport, recently bought, is equipped with power heated side mirrors but they are not working. I've checked fuses, wiring and connections. I replaced the master door panel switch. Power windows and door locks all work, the window lock button works, and all buttons are back illuminated including the mirror control buttons but the mirrors aren't responding to the controls.... any ideas?

It's very common on 97+ XJ's (Mine included) to have wiring issues in the doors. You may have a broken wire in the loom between the door and the body. There are several good write-ups on here on how to fix this, including how to access the wiring without damaging the loom boot. On my 98, the passenger side speaker cuts out from time to time. At a bare minimum, you can pull the loom back and inspec the wiring for any breaks.

Are you getting power at the mirror switch?

mirror control switch has back lighting that is working. when hitting the power window controls to roll them up for instance both front windows simultaneously, the lighting on the mirror controls dims slightly. I have not checked if there is power going to the harness that connects to the mirror. My next step was to pull all harnesses in the door and check for breaks.

I would need to look at a wiring diagram, but I don't believe the led lighting is on the same power feed as the switch itself. You need to check for power at the switch with a DVOM. If you don't have power at the switch, trace the wiring to find the break (most likely in your door jamb loom as I previously suggested)

It makes sense that the lights in the switch would dim when you run a power accessory as it is a load and a demand on the electrical system. My XJ does this as well and it's normal.

So in my continuing research and before tackling the wiring, I ran across a fuse block diagram on jeepforum.com. the diagram had a list of what each fuse controls and in the list #10 was occupied and controlled among other things; transmission and back -up switch, etc... and #18; among other things, power mirrors. The owner's manual which came with the vehicle, shows both of those fuse slots as "open". Based on the info I found on jeepforum, I put a 10a fuse in slot #10 and well, my reverse lights started working again and the radiator cooling fan started working too. I'm still getting the 705 code - transmission range sensor, but glad to have those items working again. Based on this result, I put a 15a in the #18 slot, and now my power mirrors are working. So including my manual, I found multiple diagrams showing both those slots as "open". Confusing ....