Reasons a Heater Won’t Work

Driving a vehicle without heat in the cold of winter is terrible. In addition, shivering while you drive may not be the safest way to drive. There is also the problem of your defroster not working properly, which can pose a hazard to driving. A lack of heat can be due to simple causes you can correct yourself, or more complicated ones requiring the services of Fifth Gear Automotive mechanics in Lewisville, TX. 


The heat in your vehicle is supplied by hot coolant circulating through the engine, with a small amount diverted to the heater core. It is from the heater core where your vehicle obtains its heat. There are a number of potential reasons why the heater may not be working.

Common causes for a lack of heat include a low coolant level, a clogged heater core, a heater valve may be failing to open, the doors in your vehicles HVAC system may not be operating or the thermostat may be stuck in the open position. Any of the following might be the cause for your vehicle’s lack of heat:

Low Coolant

A low coolant level is a common cause for a lack of heat. Check the level in your radiator first. However, before opening the radiator cap look for signs of leakage around the cap, as a failing radiator cap is also a potential cause of issues, including a lack of heat. It’s okay to top the coolant off in the short term, but consistently low coolant indicates a leak in the cooling system as it doesn’t simply evaporate. You may have noticed antifreeze on the ground beneath your car, and if so there is a coolant leak.

Coolant leaks may be due to a problem as simple as a loose hose clamp, or the leak may be due to a leaking hose. However, a leaking water pump, leaking radiator or a serious problem in the engine will require a professional repair before it leaves you stranded. Contact Fifth Gear Automotive to schedule service and repair with our mechanics in Lewisville, TX .

Air Pockets

An air pocket in the cooling system can interfere with the flow of hot coolant through the heater core. Air pockets can develop after coolant changes such as in a radiator flush, replacement of a water pump, lower radiator hose or other actions where the coolant was drained. Topping the coolant system off doesn’t always prevent or rid the system of air bubbles.

Open Thermostat

A thermostat can stick in the open position. You may have noticed the engine temperature is taking longer to reach its normal position, or may not be reaching it at all. In addition, a thermostat with the wrong operating temperature can also cause problems. Bring your vehicle in to our certified mechanics in Lewisville, TX for accurate diagnosis and repair.

Defective Heater Control Valve

Defective vacuum operated heater control valves are a potential cause for a lack of heat. Contact Fifth Gear Automotive mechanics in Lewisville, TX to schedule repairs.

Clogged Heater Core

Accumulated debris in the cooling system may clog the heater core and prevent coolant from entering it. If heated coolant can’t reach the heater core, your heating system will blow cool air. Following the recommended schedule of engine coolant change is the best means for preventing a clogged cooling system and heater core. Our mechanics in Lewisville, TX can take care of this for you. As with anything else, the heater core will eventually require replacement if you tend to keep your vehicles long term. Heater core replacement is often a difficult job, typically due to location and difficulty accessing. Needless to say, it isn’t a do your self job, so schedule service with your mechanic.

Electrical Problems

A defective blower motor may be the cause of the heater fan not working. Heat may be available in the heater core, but without the fan operating you won’t receive the benefit of heat inside your vehicle. Try the fan on different fan speeds, if the fan isn’t blowing properly, or at all, it is likely you need a new blower motor. In addition, when the fan isn’t operating at all, don’t forget to check the fuses and replace any that appear blown.

In addition, problems affecting other electrical components, such as a blown fuse, a defective power relay, or other electrical components are also potential causes, and should be checked by our mechanics in Lewisville, TX.

A fuse blows when a circuit overload occurs, providing protection to the wiring and other electrical components. Furthermore, fuses that blow repeatedly indicate an electrical problem. Schedule a diagnosis and repair with our certified mechanics in Lewisville, TX.

In addition, if a new fuse blows as soon as the blower is turned on, there may be a dangerous short. However, a fuse that lasts a while before blowing may indicate a worn fan motor that will need to be replaced by an ACE certified mechanic.

Water Pump

A worn and weakened water pump, or a slipping drive belt are also potential causes for a lack of heat. Contact Fifth Gear Automotive to schedule service with our certified mechanics in Lewisville, TX. 

Maintaining a routine check on the condition of belts, hoses, and providing the recommended frequency of coolant changes will go a long way in ensuring the long term performance of your vehicles cooling system. In addition, remember to provide the routine maintenance task of the weekly fluid level check on your vehicle. Consistently low levels are an effective means of recognizing a problem.

There is no reason for you to endure the winter without adequate heat in your vehicle. You can rely on the integrity and expertise of our ASE certified mechanics in Lewisville, TX to provide a professional diagnosis and reliable repairs for your vehicle. Make Fifth Gear Automotive your one stop shop for installation, service, diagnosis and repair you can count on. Contact us today to schedule the automotive services you require.