If you mean the fan - replace the fan speed resistor if the fan only works on high speed. Please supply more information - no heat or cooling? Does fan work? Does mode switch work?
On a 2000 Mercury Cougar : That's your Anti-theft system status light
Your thermostat is stuck open.
http://www.coolcats.net/tech/troubleshooting/heatercore.html
To change the heater core on a 1988 Mercury Cougar, first ensure the engine is cool, then disconnect the battery. Remove the dashboard and the center console to access the heater core housing. Disconnect the hoses from the heater core, remove the mounting bolts, and take out the old core. Install the new heater core by reversing the disassembly steps, reattach the hoses, and reassemble the dashboard and console.
the air conditioner and heater are two separate things.(not connected) ;) it may have a fuse. or the it could just be bad.
You can find this information from John Sherbit-MOTOR MANUAL/MOTORALLDATA Distributor
Yes, the 1993 Mercury Topaz is equipped with a blower motor relay that controls the operation of the air conditioner and heater. The relay is typically located in the fuse box under the hood of the vehicle. If you are experiencing issues with your air conditioner or heater not working, the relay may be a possible culprit to check.
You can find this at you local public library...........
What you may be experiencing is a blown resistor. If the heater only works when on 4, but not 3, 2, or 1, then it is most definitely the answer. If it is, there is plenty of info on this at newcougar.org.
When the heater resistor goes, your climate control fans will only work on the fourth setting. You can get a new resistor from any Ford Lincoln Mercury dealer, though they may have to order one.
To replace the heater motor on a 1999 Mercury Cougar, first disconnect the negative battery cable and remove the passenger side lower dash panel for access. Next, locate the heater motor, which is typically found near the firewall. Disconnect the electrical connector and remove the mounting screws to take out the old motor. Install the new heater motor by reversing the process, ensuring all connections are secure before reassembling the dash panel and reconnecting the battery.
Try this link http://members.tccoa.com/timb/Heatercore.htm its for a 94 Thunderbird but it worked for my 95 Cougar. It has description and pictures. It's a tough project, make sure you have help. Good Luck!