Originally Posted by Motorcharge
I've since replaced the radiator and aux fan. Backflushed the system prior to installing the new radiator and backflushed the heater core again on it's own. New rad is in, aux fan works. Same situation. Put an IR gun on it today, it's definitely not running hot or anywhere close to what the gauge is reading.
So now you have confirmed you have a guage problem. As others suggested, the cheaper of the two major elements of the temperature guage system is the sender. Get a new one, and preferably from Mopar, as it's most likely to be properly calibrated to work with a known good guage correctly.
1992 XJ 2" lift -- RIP
2000 XJ 3" lift -- Australian Ford Big Brakes up front, rock rails, ZJ rear discs (with WORKING parking brake), C4x4 rear bumper/tire carrier, Hella H4 headlights, IPF driving lights, OEM skid plates, OME springs/shocks, JKS LCA's, JKS Sway Bar links.