Yeah, trying to troubleshoot Jeep electrical problems without a multimeter is like trying to change a water pump without a set of wrenches - you can sometimes do it without the right tools, but it's going to make your life a lot harder. Fortunately, they can be bought cheaply - Canadian Tire puts theirs on sale for around ten bucks every 0nce in a while, so I have one in the shop and one in the Jeep, just in case.