Sounds like a blower resistor.
Instruction for how to replace this resistor can be found in the link below. Thanks to newcougar.org user Goldie for the How-To.
http://tutorials.newcougar.org/HowTofixheaterblowerresistor.pdf
Why are you replacing the switch? If the fan works only on high speed, replace the fan resistor. There was a TSB for this.
take to dealership. there was a recall and they will fix it for free.
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.
On a 2000 Mercury Cougar : The OIL PRESSURE warning light is located on the right side of your gauge cluster just above the red " BRAKE " warning light It looks like an oil can Just before you start the car , when the ignition key is turned to the RUN position , the light should light up for a few seconds to prove that the bulb works
Your brake light ignition switch should be replaced. It works your brake lights and ignition switch, so you do need it. It only costs about $7 dollars.
Do an online search to get the following links that have posts about how ductless air conditioning works- http://www.ehow.com/how-does_4811846_ductless-air-conditioning-work.html; http://www.ductlessdepot.net/standart-47.html; http://www.ductlessdepot.net/standart-40.html
Yes, this prevents your air conditioning system from freezing over, similar to a frost free fridge. almost every air conditioning system works like this.
If it works properly, never.
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?
a Blocked heater core
There is mercury the thermometer. (well, some thermometers..) when mercury gets hot it expands because mercury is a metal. I'm pretty sure.
There are two sensors on the door of a Mercury Cougar; the first which controls the two stage interior lighting can be found on the forward portion of the door jamb it is a button. The second sensor is found the the door latch mechanism at the rear of the door jamb. It is problematic at best. Use some wd40 to clean it really spray it well. Then use a lubricant spray; silicon spray works the best. Really saturate it well. You will probably have to do this annually. There are two sensors on the door of a Mercury Cougar; the first which controls the two stage interior lighting can be found on the forward portion of the door jamb it is a button. The second sensor is found the the door latch mechanism at the rear of the door jamb. It is problematic at best. Use some wd40 to clean it really spray it well. Then use a lubricant spray; silicon spray works the best. Really saturate it well. You will probably have to do this annually. There are two sensors on the door of a Mercury Cougar; the first which controls the two stage interior lighting can be found on the forward portion of the door jamb it is a button. The second sensor is found the the door latch mechanism at the rear of the door jamb. It is problematic at best. Use some wd40 to clean it really spray it well. Then use a lubricant spray; silicon spray works the best. Really saturate it well. You will probably have to do this annually.