Logo Automobile Information Add Site to Favorites  
Auto Repair
Auto Repair Home
Auto Repair Ask a Car Repair Question
Auto Repair Car Question Forum
Auto Repair Questions by Manufacturer
Auto Repair Questions by Topic
Auto Repair First Things to Check
Auto Repair How to Repair or Service
Auto Repair Car Repair Manuals
Auto Repair How Does it Work
Auto Repair Car Repair Video Series
Auto Repair Auto Maintenance
Auto Repair Car Sound Problems
Auto Repair Auto Term Abbreviations
   
   
 
Popular Site Links

  

Auto Repair Automobile Safety Inspection
Auto Repair Brake Replacement Guides
Auto Repair Service Engine Soon Light
Auto Repair Belt Routing Diagrams
Auto Repair Avoid Car Repair Rip Offs
Auto Repair Trouble Code Table
Auto Repair How to use Diagnostic Tools
Auto Repair Smog Test Preparation
Auto Repair Hybrid Car Information
Auto Repair Test Equipment Store
Auto Repair Auto Parts
 
Search Website
 
 
Recent Repair Topics

 

Auto Repair1996 Chevy Lumina 96 Lu...
Auto Repair1985 Oldsmobile 98 Roug...
Auto Repair2000 Ford Crown Victoria...
Auto Repair1985 Chevy Silverado Ch...
Auto Repair2001 Ford F150 Rattling...
Auto Repair1992 Ford Station Wagon ...
Auto Repair1991 Toyota Camry No Fi...
Auto Repair More Repair Topics...
 


     
       


Free Car Repair Advice by Certified ASE Technicians



How Does it Work / Heater

How a Car Heater Works

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 trouble-shooting. 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.  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 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.  If there is too little coolant in your car’s 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 1)  engine block 2) thermostat 3) the upper and lower hoses leading respectively into and away from the 4) radiator; 5) the radiator cap; 6) the radiator fan; 7) the water pump and, going from the engine block towards the passenger cabin; 8) the heater core and its associated hoses and fan.

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
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, 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 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
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.

How Does it Work / Heater

Check Manufacturer Specific Heater Questions and Answers

Related Subjects

Got a Car Repair Question we will answer it for FREE!

GET A REPAIR MANUAL FOR YOUR CAR. Get instant access to your vehicles drive belt routing, wiring diagrams, trouble code information and other available updates and factory bulletins.





     
Popular Service Repairs
Test Fuses
Replace Front Brake Pads
Check Engine Light
Rear Brake Shoes
Rear Brake Pads
Test Alternator
Replace Air Filter
Test Battery
Tune Up
More Service Repairs...
Advertisement
Car Questions
Acura
Alfa Romeo
American Motors
Audi
BMW
Buick
Cadillac
Chevy
Chrysler
Citron
Daewoo
Daihatsu
Dodge
Eagle
Ferrari
Fiat
Ford
Geo
GMC
Honda
Holden
Hummer
Hyundai
Infiniti
International
Isuzu
Jaguar
Jeep
Kia
Land Rover
Lexus
Lincoln
Mazda
Mercedes Benz
MG
Mercury
Mini
Mitsubishi
Nissan
Oldsmobile
Opel
Peugeot
Plymouth
Pontiac
Porsche
Renault
Rolls Royce
Rover
Saab
Saturn
Scion
Seat
Skoda
Subaru
Suzuki
Toyota
Vauxhall
Volkswagen
Volvo

Home l Help l Privacy Policy l User Agreement l About Us l Computer Repair Question l Contact Us l Link to Us l We're Hiring l Affiliate Program
  Copyright © 1999 - 2009 2CarPros.com - Professional Mechanics Online