Tech

When Your Car Heater Blows Cold Air

Oh baby, it’s cold inside

Car heaters can fail in a number of ways, but if you blow cold air, the two causes are either the coolant is not flowing through the heater core or the air from the blower motor is not passing the heater core. Other underlying issues can cause your car heater to stop working suddenly, but you will usually deal with one or the other of these two causes.

man in a car driving in the snow

Tuomo Binamo/Folio Images/Getty Images

This provision applies to vehicles with water-cooled engines and does not apply to driving older Volkswagens or new electric vehicles with air-cooled engines.

Crash process in car heater operation

Most cars on the road have a water-cooled engine, and the heating system works on the same basic principle. The engine’s hot coolant flows through a heater core that looks and functions like a small radiator, and a blower motor lets air through. The coolant heats the air, which in turn heats the interior of the vehicle.

Because of this, it takes time for the heater to start blowing warm air. The heater core has no heat to extract until the engine is warmed up. A clogged heater core, stuck thermostat, or air in the cooling system can also cause your car heater to cool down.

A problem with the cooling system causes the car heater to get cold.

There are four major cooling system issues that can cause your heater to blow out cold air:

  • caged thermostat
  • air in the cooling system
  • clogged heater core
  • Coolant does not flow through heater core

It’s actually a little more complicated, but this is the most common heating problem.

caged thermostat

A thermostat is a valve that opens and closes according to the temperature of the coolant. When the engine warms up, it stays closed until the engine’s coolant reaches a certain temperature range. If it does not open, the coolant may not circulate properly, the engine may overheat, and the heater may have problems blowing out cold air.

Leaving the thermostat open may prevent the engine from warming up properly or prolong the warm-up period. If the heater is blowing lukewarm air instead of cold air, an open thermostat may be clogged.

air in the cooling system

Another common problem arises when air enters the cooling system. Because the heater core is often the highest point in the cooling system, air can flow inside and become trapped. In this case, you need to wash the air bubbles to solve the problem.

clogged heater core

A clogged heater core can also cause your car’s heater to get cold. This is best checked with a non-contact thermometer. This ensures that the coolant is flowing through the heater core. If not, flushing the heater core often solves the problem.

Some vehicles have valves installed in the heater core intake line that are operated by vacuum or mechanical cables. Another reason why car heaters get cold when this valve is closed.

No coolant flow through heater core

A heater core can become clogged in several ways. When you hear about a clogged heater core, it usually means that corrosion or other debris is clogging the inner pipe, and flushing often solves the problem. However, the fins on the heater core can also become clogged with lint, pine needles, and other debris that can get into the heater box. The solution to this is to open or remove the heater box and clean the fins.

Other Reasons Your Car Heater Gets Cold

Most of the causes of car heaters getting cold are related to the heater core. However, there may also be mechanical, electrical, or vacuum issues. The details vary widely from vehicle to vehicle, but most systems have a mixing door that changes the way air flows through the heater core or not.

It doesn’t matter whether the heater core is working properly even if the mixing door is jammed. When the blend door is stuck, the heater core is essentially bypassed and you can’t feel anything but cold air.

Mixed statements can be anchored for a number of reasons and are not always anchored in the same way. It’s stuck open so it’s always warm or partially closed to give you only tepid heat.

Blend doors can also become jammed due to loose mechanical connections or vacuum lines, faulty switches, or many other reasons. If you suspect a problem with the mixing door, the specific diagnostic procedure depends on how your vehicle’s heating system is set up.


More information

When Your Car Heater Blows Cold Air

Oh, baby, it’s cold inside

A car heater can fail in several ways, but when it blows cold air, the two likely causes are that the coolant isn’t flowing through the heater core or air from the blower motor isn’t being directed through the heater core. Typically, you will be dealing with one or the other of these two causes, although other underlying issues can lead to a car heater that suddenly stops working.

 Tuomo Vainamo / Folio Images / Getty ImagesThis article relates to vehicles with water-cooled engines and doesn’t apply if you drive an old Volkswagen with an air-cooled engine or a new electric car.
Crash Course in Car Heater Operation

Most cars on the road have water-cooled engines, and their heating systems work on the same basic principle. Hot coolant from the engine passes through a heater core, which looks and functions like a small radiator, and a blower motor forces air through it. The coolant then heats the air, and the air, in turn, warms the interior of the vehicle.

This is the reason that it takes a while for heaters to start blowing warm air. Until the engine warms up, there’s no heat for the heater core to extract. It’s also the reason that a plugged heater core, stuck thermostat, or air in the cooling system can cause a car’s heater to blow cold.

Car Heater Blowing Cold Due to Cooling System Issue

The four main cooling system problems that can cause a heater to blow cold air are:

Stuck thermostat
Air in the cooling system
Plugged heater core
Coolant not flowing through the heater core

It’s a little more complicated than that in practice, but these are the most common heater issues that you’ll run into.

Stuck Thermostats

Thermostats are valves that open and close depending on the temperature of the coolant. As the engine warms up, they stay closed until the coolant in the engine reaches a specific temperature range. If they fail to open at that point, the coolant won’t circulate properly, the engine may overheat, and you might experience a problem where the heater blows cold air.

When a thermostat sticks open, it can prevent the engine from warming up properly or prolong the warming-up period. If the heater is blowing lukewarm instead of cold air, a stuck open thermostat could be the cause.

Air in the Cooling System

Another common problem occurs when air gets into the cooling system. Since the heater core is often the high point in a cooling system, air can move into it and become trapped. If that’s the case, the air bubbles must be flushed out to fix the problem.

Plugged Heater Core

Plugged heater cores can also cause a car’s heater to blow cold. The best way to check for this is with a non-contact thermometer. You use it to check whether coolant is flowing through the heater core. If it isn’t, flushing the heater core often fixes the problem.

Some vehicles have a valve installed in the heater core inlet line that is operated by vacuum or a mechanical cable. If that valve is stuck closed, that’s another reason a car heater will blow cold.

Coolant Not Flowing Through the Heater Core

A heater core can become plugged in more than one way. When you hear about a plugged heater core, that usually means that corrosion or other junk has clogged up the internal tubes, and flushing will often clear it up. However, the fins of a heater core can also be clogged with lint, pine needles, and other detritus that manage to get into the heater box. The fix for this is to open or remove the heater box and clean the fins.

Other Reasons a Car Heater Can Blow Cold

Most of the reasons a car heater blows cold have to do with the heater core. Still, you can also have a mechanical, electrical, or vacuum problem. The specifics vary significantly from one vehicle to another, but most systems have a blend door that changes how air flows or doesn’t flow through the heater core.

When a blend door is stuck, it doesn’t matter if the heater core is working perfectly. Since the blend door is stuck, the heater core is essentially bypassed, and you won’t feel anything but cold air.

A blend door can stick for a number of reasons, and they don’t always stick the same way. It can be stuck open, resulting in all heat all the time, or stuck partially closed so all you get is lukewarm heat.

A blend door can also be stuck because of mechanical linkage or a vacuum line coming off, a switch going bad, or several other reasons. If you suspect a blend door issue, the specific diagnostic procedure depends on how your vehicle’s heating system is set up.

#Car #Heater #Blows #Cold #Air

When Your Car Heater Blows Cold Air

Oh, baby, it’s cold inside

A car heater can fail in several ways, but when it blows cold air, the two likely causes are that the coolant isn’t flowing through the heater core or air from the blower motor isn’t being directed through the heater core. Typically, you will be dealing with one or the other of these two causes, although other underlying issues can lead to a car heater that suddenly stops working.

 Tuomo Vainamo / Folio Images / Getty ImagesThis article relates to vehicles with water-cooled engines and doesn’t apply if you drive an old Volkswagen with an air-cooled engine or a new electric car.
Crash Course in Car Heater Operation

Most cars on the road have water-cooled engines, and their heating systems work on the same basic principle. Hot coolant from the engine passes through a heater core, which looks and functions like a small radiator, and a blower motor forces air through it. The coolant then heats the air, and the air, in turn, warms the interior of the vehicle.

This is the reason that it takes a while for heaters to start blowing warm air. Until the engine warms up, there’s no heat for the heater core to extract. It’s also the reason that a plugged heater core, stuck thermostat, or air in the cooling system can cause a car’s heater to blow cold.

Car Heater Blowing Cold Due to Cooling System Issue

The four main cooling system problems that can cause a heater to blow cold air are:

Stuck thermostat
Air in the cooling system
Plugged heater core
Coolant not flowing through the heater core

It’s a little more complicated than that in practice, but these are the most common heater issues that you’ll run into.

Stuck Thermostats

Thermostats are valves that open and close depending on the temperature of the coolant. As the engine warms up, they stay closed until the coolant in the engine reaches a specific temperature range. If they fail to open at that point, the coolant won’t circulate properly, the engine may overheat, and you might experience a problem where the heater blows cold air.

When a thermostat sticks open, it can prevent the engine from warming up properly or prolong the warming-up period. If the heater is blowing lukewarm instead of cold air, a stuck open thermostat could be the cause.

Air in the Cooling System

Another common problem occurs when air gets into the cooling system. Since the heater core is often the high point in a cooling system, air can move into it and become trapped. If that’s the case, the air bubbles must be flushed out to fix the problem.

Plugged Heater Core

Plugged heater cores can also cause a car’s heater to blow cold. The best way to check for this is with a non-contact thermometer. You use it to check whether coolant is flowing through the heater core. If it isn’t, flushing the heater core often fixes the problem.

Some vehicles have a valve installed in the heater core inlet line that is operated by vacuum or a mechanical cable. If that valve is stuck closed, that’s another reason a car heater will blow cold.

Coolant Not Flowing Through the Heater Core

A heater core can become plugged in more than one way. When you hear about a plugged heater core, that usually means that corrosion or other junk has clogged up the internal tubes, and flushing will often clear it up. However, the fins of a heater core can also be clogged with lint, pine needles, and other detritus that manage to get into the heater box. The fix for this is to open or remove the heater box and clean the fins.

Other Reasons a Car Heater Can Blow Cold

Most of the reasons a car heater blows cold have to do with the heater core. Still, you can also have a mechanical, electrical, or vacuum problem. The specifics vary significantly from one vehicle to another, but most systems have a blend door that changes how air flows or doesn’t flow through the heater core.

When a blend door is stuck, it doesn’t matter if the heater core is working perfectly. Since the blend door is stuck, the heater core is essentially bypassed, and you won’t feel anything but cold air.

A blend door can stick for a number of reasons, and they don’t always stick the same way. It can be stuck open, resulting in all heat all the time, or stuck partially closed so all you get is lukewarm heat.

A blend door can also be stuck because of mechanical linkage or a vacuum line coming off, a switch going bad, or several other reasons. If you suspect a blend door issue, the specific diagnostic procedure depends on how your vehicle’s heating system is set up.

#Car #Heater #Blows #Cold #Air


Synthetic: Vik News

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I'm Do Thuy, passionate about creativity, blogging every day is what I'm doing. It's really what I love. Follow me for useful knowledge about society, community and learning.

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