The blower works sometimes at all speeds and sometimes it won't work at all. It is completely unpredictable. Help new out here, please.
There are two primary items that would be common to a problem at all speeds, the fan speed switch and the fan motor itself. The resistor pack is not in the circuit on the fan's highes speed setting. Check the wiring between the switch and motor for being burnt, melted, etc. as suggested above. That is a very real problem, especially for older TJs, my '97 fan motor wiring looked like it had been in a forest fire & I had to replace much of it.
If the wiring is ok, I would probably lean more towards a bad fan motor or perhaps a bad connection.
Okay, so based upon your info and my lack of knowledge, it sounds like a bad motor is not likely. I will pull the motor and test it, but I should ask a question or two before I contort myself into that position again.It is the ground side that you need to check. The ground path goes from the motor through the resistor (high speed bypasses the resistor) through the speed switch & through the mode switch.
This is an old thread so you may not get the OP to answer but if you have power to the blower (fan) motor then you are losing your ground. The motor is speed controlled from the ground side of the circuit through the resistor block, the speed switch & the mode switch. Any of these 3 components may be bad but often it’s one of the connectors or the wiring that overheats & you can see melting if you check closely. Sometimes one of the terminals is “loose” fitting inside the connector & arcs causing loss of contact so careful inspection is needed. Read this thread for detailed troubleshooting of the circuit. In post #3 there is a link to a knowledge base that has FSMs & you can see the wiring diagram for the circuit there. Read the first 10 posts & I think they will help find your problem.