I just bought my second 5.9L ZJ (this one is for play, my old one is pretty much going to be living most of its life on pavement and snow now). Both have cruise control issues. The first just takes a finesse with the on/off button. But this one just plain won't come on - although the previous owner says with enough work, it will come on. Is this a common switch issue for Grand Cherokees?

 

It is fairly common. There was a write-up about cleaning the contacts in the switch, but I don't remember where I saw it.

 

The cruise control switches are not a simple on/off contact type of switch, they send a resistance signal to the computer and then the computer can tell what switch it is by the amount of resistance that is read because each switch is rated different. It is possible after time and years of dust and muck getting into the switches can cause the resistance value to change and send wrong signals to the computer. www.rockauto.com may have new switch assemblies for you.