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Are you thinking blower "switch" or blower motor resistor? Does your Explorer have the manual temp controls or the Electronic Automatic Temperature Controls (EATC)? $100 for a resistor set seems high....
Does the blower work only on High speed but not on any of the lower speeds? If so, it's probably the resistor set. If you have no operation on any speeds, it's not likely the resistor, more likely the blower motor or possibly the blower motor relay.
The thermal fuse in the blower motor resistor is easily tested with a continuity tester. If you determine it is just the thermal fuse and you opt to attempt to save the $23, make sure to get a thermal fuse of the same temperature rating and DO NOT solder it in place. Soldering them will likely take some of the life out of them and, worst case, will cause it to open. You can try using clip on heatsinks when soldering, but it's still not as good as crimping them in place like the original installation.