One problem related to underhood wiring has been reported for the 1999 Jeep Wrangler. The most recently reported issues are listed below.
1st issue: the dash gauges will go off and on intermittently. I have fought with this problem for years now. The dealer of course doesn't know what I'm talking about. Never heard of it. I have completely removed the dash looking for problems. Bad grounds? I can't tell where. I suspect the plugs the cluster slips into. I've tried to pull the mounts closer for a better connection. It seamed to work for a while. Then it comes back. A good sound beating on the dash brings them back on. Amazing what that plastic will take. All this started after the warranty expired. I refuse to take it in and pour money at it till they figure it out. All I want is to know how to fix the gauges. I'm about ready to cut the wires and solder them directly on. 2nd issue: I began smelling plastic burning or something. Later the heater fan quit working. After some reading of the service manual, I checked a lot of parts and found the control/selector switch unit heated up and partially melted the wiring harness as well as burnt inside the unit. Bought another and replaced it. Works great now. All the fan positions work again. This switch has to be replaced so often I just leave the screws from the center dash panel off. Every 99 Jeep Wrangler owner I know has the exact same problems. Does someone have to die before there is a fix/recall? nothing like driving down the road and smell an electrical fire when you are 100 miles from anyone.