Could be the switch or the resistor and or the fan itself , There was a recall on this but to late to get it now , All are easy fixes
location of relay blower motor 1997 Mercury mystique
There is none - usually it is the module in the top of the heater / blower box (resistor module) that is the problem.
If the blower works on some speeds and not on others, you may not need a motor. Instead, you may only need a new blower motor resistor.
It's on the fuse panel under the right side of the dash.
To remove the blower motor from a 1998 Mercury Mystique, first, disconnect the negative battery cable to ensure safety. Then, access the blower motor by removing the passenger side lower dash panel and any necessary trim pieces. Disconnect the electrical connector from the blower motor, remove the mounting screws, and carefully pull the blower motor out of its housing. Finally, reverse these steps to install the new motor if replacing it.
Look under the dash on the passenger side
2004 ford expedition front blower not working
To replace the blower resistor on a 1998 Mercury Mystique, first, disconnect the negative battery cable for safety. Locate the blower resistor, which is typically found behind the glove compartment or under the dashboard on the passenger side. Remove the screws securing the resistor, disconnect the wiring harness, and then install the new resistor by reversing the removal process. Reconnect the battery and test the blower motor to ensure proper operation.
Had same problem in 2002 Pontiac Gran Prix. The blower motor has two parts, one for settings 1-4 and one for setting 5. This was a sensor problem, not a fuse problem. Dealer service writer was familiar with problem. Repair about $110. at dealership
Did you already replace the heater blower resistor? I only paid 30 bucks for a replacement at Cut Rate Auto Parts. Mine was rusted and broken.
The resistor is located on the duct work under the dash. Sitting in the passenger seat facing forward it is to the left of the blower motor mounted on the duct work firewall.
See related link. Click on Owner Guides The owners manual ( which includes the fuse panel diagram ) can be viewed on-line