The Mercury Tracer heater core can be found behind the passenger side kick plate. The heater core can be removed by disconnecting the water supply lines and removing the retaining bolts.
the heater blower resistor is located on the passenger side footwell near the firewall. a complete how-to replace the resistor, along with photos is available on newcougar.org http://www.newcougar.org/forums/how-tos/3732-fixing-heater-blower-resistor-install-photos.html
If it is defective it will need to be replaced.
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.
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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.
How much will it cost me to replace the heater core in my 1999 Mercury
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Replace heater motor resistor.
A bad heater blower motor resistor would effect one or more blower speeds other than high.
The heater resistor is quite simple to change. Unplug the wiring harness from the heater resistor. Remove the heater resistor retaining screws. Reverse the process to install your new heater resistor.
It is the resistor, replace it.