Without the heating and air conditioning systems in today’s modern
vehicles, we would all be miserable driving to our destinations. We take
for granted the heat that keeps us warm in the winter months, and the
cool air that refreshes in the summer time. Let’s take a look at how both
systems work to keep us comfortable all year round.

   
The heater in your car is basically a smaller version of your cooling
systems radiator. Hot engine coolant is circulated through a small radiator,
often times called a heater core. A fan is positioned in front of the
heater core to blow cold outside air over the fins. As this air travels
over the heater core, it heats up and becomes the hot air which blows
out your heater vents.

   
Like your engines cooling system radiator, the heater core can
suffer some of the same issues. If the heater core becomes clogged with
rust or sludge, you will no longer have heat. Also leaks can cause a cabin
full of white steam and really mess up your windows. If you smell the
sweet aroma of coolant when your heater is on, chances are, you have a
small leak in the heater core. Often times the heater core is buried under
the dashboard, and replacing it, is a major job.

   
The air conditioning system in your car is comprised of a compressor,
condenser, expansion valve and evaporator. If you have ever used a can
of compressed air to clean computer components, you will know that the
bottle gets very cold in a short amount of time. This is due to the rapid
expansion of the compressed gas. The same thing happens in your car’s
air conditioning system. Refrigerant (AKA Freon) is compressed in the
compressor and turns into a hot gas. In the condenser, this hot gas is
cooled to a liquid state and travels to the expansion valve. As the Freon
goes through the expansion valve it returns to a low-pressure gas and
rapidly cools in the evaporator. A fan blows over the evaporator and cools
the air that eventually blows out your vents.

Click
Here For An Excellent Illustration and Further Explanation.

Common Problems:

• From time to time
  the A/C system needs to be recharged to bring it back up to maximum
  efficiency.  Sometimes a leak may cause loss of refrigerant and
  will need to be fixed before refilling.  It's difficult to tell
  if a leak is present without specific test equipment so let it up to
  a professional. 
  
• In recent years,
  the EPA has phased out the use of R-12 Freon in all refrigeration systems
  and R-134 has become the new standard.  If you have an older system
  with R-12 you may need to retrofit your system to handle the new R-134
  refrigerant.  Sometimes seals, hoses and even the compressor need
  to be changed.  The problem arises when the older seals and hoses
  are not compatible with the new oils found in the R-134.
  
• Corrosion will
  cause the heater core (secondary radiator) to leak.  This will
  manifest itself by leaving steam into the passenger compartment and
  fogging your windows.  You will know there is a leak by the sweet
  smell coming from your vents.  Unfortunately changing the heater
  core is usually not the easier job in the world as engineers tend to
  squeeze them into some pretty tight spaces under the dash.

The HVAC system is
one of the most least understood systems in your vehicle and let the professionals at Majestic handle your HVAC needs.

source:www.AutoEducation.com