I have a 1999 Jeep Wrangler Sport 4.0L with a kind of serious problem. My wipers dont always work. Sometimes they work fine, sometimes they work fine to start with and then quit without warning, other times the only way to get them to turn on is to turn them on high and then go to the speed that I want to use. It has the intermittent option but I am not yet convinced that that has anything to do with my problem. They will quit working some of the time while using the delay but they also quit on low sometimes. I have been through and checked all of the plugs, and even went as far as to grease them up so I know they are making good connections. I'm at a loss, I would think if it were the motor or the switch it would just go out all together. And if it were a broken wire, wouldn't it come on and go off if I hit a bump in the road? They shut off on smooth roads so bumpy or smooth does not matter. Please help!I would assume the problem is either with the motor or the switch. You can test these units with your multimeter or test light.
In your garage or driveway, turn on the wipers and operate them until they fail. (Keep your windshield wet during this operation.) Then pull apart the electrical connection and test for +12 volts where it ought to be. If there is no juice, assume a bad switch. If you have good voltage, the motor is likely bad, but first verify a good ground.
You ought to be able to find used parts after you figure out what you need.