Before trying to fix your car's heater,
you should understand how your car's heater system works. On this page, an explanation
of how your car's heater system functions, and then, further down, some pointers
on heater system troubleshooting. A car heater is designed to warm the passenger
cabin of your car; this system makes use of excess heat from the
engine's internal combustion process.
A car's engine, in fact, when in operation produces so much excess heat that if
excess heat is not removed, it would destroy the engine. It is your car's cooling
system that removes the excess heat; some of an engine's excess heat is released
through the exhaust system.
Most of the rest of an engine's excess heat is absorbed by a circulating liquid
coolant, a mix of water and antifreeze.
The heated liquid coolant is carried from the engine through the hoses to the
radiator, which transfers the heat
from the coolant to the outside air through a convection process. The heater core
in your car is similar to the radiator in the front of your car; in fact it looks
like a small radiator. The difference is the heater is mounted inside the car and
air is blown through the fins of the core. The heater hoses transfer engine coolant
to the heater core, this allows the heat from the engine coolant to be utilized
and warm the passenger compartment air.
The heat transferred lowers the temperature of the liquid coolant, which is then
circulated back to the engine to absorb excess heat again, a continuous system.
Whereas the radiator is located at your car's front grill, the unit that transfers
heat to the passenger cabin (heater core) is located inside the dashboard near the
air cabin filter. This
unit, something of a mini-radiator, is referred to as the heater core. Heated liquid
coolant circulates through tubes in the heater core, and a heater fan blowing across
those tubes, as well as through little fins encasing the tubes, directs warmth through
the heating vents into your car's passenger cabin.
Heater Core
Heater Problems
Because your car's heating system works off of the
cooling system, sometimes,
heating system malfunctions are caused by problems in the cooling system. One of
the first things to check when your car heater is not working is your
engine coolant level. If your car
has a coolant leak in the cooling
system, the heater will not be able to produce adequate heat. In any event, to keep
your car running optimally, you should regularly check the coolant level. For safety
reasons, this absolutely must be done only when the engine is completely cooled
down. This safety point cannot be over-emphasized.
Opening the cooling system of a hot engine presents a terrible burn hazard, as
the fluid in your car's cooling system is dangerously hot and pressurized when the
car has been in operation. It is best to let the car cool overnight before inspecting
the coolant level. Most cars have coolant reservoirs with opaque white plastic tanks
and measuring lines allowing you to see if the coolant is at the recommended level.
Coolant expands when heated, and for that reason, most coolant reservoirs have a
Full-Cold and a Full-Hot line.
If there is too little coolant in the reservoir, you should be alert to the possibility
that there could be a leak somewhere
in your car's cooling system, but you may nonetheless remove the reservoir cap and
add coolant to the Full-Cold line. Obviously, if a very short time after you refill
the coolant reservoir, the coolant level is low, there is a leak in your car's cooling
system. Many points in your car's cooling system are liable to develop leaks through
which coolant can escape. Too little coolant in the cooling system will result in
a malfunctioning heater. To inspect for a leak in your car's cooling system, you
should understand that the main physical components involved in the cooling system:
A leak in the heater core occurs most often in escaped coolant on the front passenger-side
floor of the passenger cabin. Most automobile antifreezes are either green or red,
though they might also be another color, and that despite a sweet smell they are
toxic and should never be ingested. Particular care must be taken to dispose of
used coolant properly, as the sweet smell can attract children and pets, and disposing
of used coolant at random contaminates the environment. The best way to repair a
leaking heater core is to replace the core. Even more common than a leaking heater
core, however, are leaking heater core hoses.
Car Heater Hoses
The heater hoses are held in place by spring loaded hose clamps and can be removed
with the proper tool. Visible signs of leakage are the most obvious indicator of
heater hose leaks, but you should also physically inspect the hoses for signs of
deterioration. Squeezing one hose at a time, you should feel that the hose is soft
and flexible. There should not be any irregular bulges in the hoses. You should
not feel any dry rot, which manifests as brittleness and/or cracking or weaknesses
in the hoses. If you detect any of these conditions the hoses must be replaced.
Consult your owner's manual or
service manual,
as it will likely have details specific to your car's heating system.
Before you replace any hoses measure the length and diameter of your old hoses
so you will know the size your new ones must be. Many cars use three different sizes
of heater hoses; the standard diameters are 1/2", 5/8" and 3/4". When removing the
old hoses, take care not to use any yanking or turning motion that could damage
the heater core. Repair technicians often score the old hoses open with a blade
and then gradually coax them loose before removing them.
Controlling the heater system varies in most cars, but primarily there are two
designs, the first design is the "manual control system", which constantly requires
manual adjustment from the driver to maintain the desired temperature. And the automatic
temperature control system which is a computerized management system, this system
can keep the cabin at a selected temperature or split the set temperature from the
driver or passenger side compartments. When a heater core fails it can leak coolant
inside the car on the driver or passenger side floor board. Replacing a heater core
is different on every vehicle, for the exact procedure on your particular car consult
a repair manual.
Replacement can vary from undoing 5 screws and replace it, to the " they
started with the heater core, then, built the rest of the car" kind of job which
removing the entire dash is not unheard of and can take many hours. A heater control
valve is used to stop the coolant from flowing into the heater core when the heater
system is off or the air conditioner is turned on. When the engine is cold the heater
will not work a heater core must have heated engine coolant to work.
Heater Control Valve
Common Problems
- When a vehicle is low on coolant it can cause the heater to stop functioning.
- When the car is running you can hear
bubbles flowing through the heater
core, (like a fish tank) this is due to air becoming trapped inside the heater
core, in time the air should dissipate to silence the noise.
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