My heater is blowing cold air.

My heater is blowing cold air. I think it's the thermostat. Should I check the engine fluids first?

My car has 57000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
If the engine temperature is not abnormally low, then a stuck open thermostat is not likely to be the cause of inadequate cabin heat. Common causes of no cabin heat include malfunctioning blend door(s) (part of the in-dash ventilation network), a faulty or stuck heater control valve, a plugged heater core, stuck open engine cooling thermostat, collapsed hoses, and low coolant level. The cost to resolve the problem depends on which of the foregoing faults is the cause. If you desire a diagnostic to determine exactly why there is no cabin heat, please request a non functioning cabin heater diagnostic and the responding mechanic will come right to your location and get this resolved for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

If your coolant level is a-okay, but your car heater is blowing cold air and your engine is overheating, then you have a clog in your cooling system. Conversely, if your engine temperatures are unrealistically low after a drive, your thermostat is likely the culprit.
The most common reasons a Ford Mustang heater isn`t working are a broken heater blower motor, a problem with the thermostat, or a failed heater blower motor resistor. Search our network of RepairPal Certified shops near you to speak with a technician about your issue. Oops!
If you find that your car heater system is blowing air but that your car is not heating up: There could be a blockage or other problem stopping heated antifreeze from moving through the heater core component. A valve or switch could be faulty, or the heater core could be a clogged.
Here are some of the most common causes of why air doesn`t flow out of your vehicle`s vents: Your air intake is clogged, meaning that air isn`t getting in from the outside at all or isn`t circulating properly. There is a blown fuse in the ventilation system. Electrical issues such as a bad relay.
A malfunctioning thermostat, no matter what kind it is, can cause a number of problems for your heater, ultimately hurting its effectiveness and efficiency. For instance, a thermostat sending incorrect signals—or no signals at all—can result in a heater that won`t even start up.
The most common cause of a vehicle`s air conditioner not getting cold enough is that it needs to be recharged. You can recharge your refrigerant by yourself, but to save time and make sure the job is done correctly you should make an appointment with your local professional auto shop.
If you find your furnace blowing cold air, you may have a dirty or clogged air filter. To make sure, remove the air filter and inspect it. If it`s clogged with dust, clean it with compressed air or wash it in warm water with mild soap or just buy a new one.
A faulty or broken thermostat is the most common cause of your car`s failing heat. Stuck open or stuck closed, the part can not only cause issues with your heat but also with your engine`s cooling system.
Across almost all models of cars and trucks, the number one cause for a vehicle`s heater to stop working is a faulty or broken thermostat.
If you find your furnace blowing cold air, you may have a dirty or clogged air filter. To make sure, remove the air filter and inspect it. If it`s clogged with dust, clean it with compressed air or wash it in warm water with mild soap or just buy a new one.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My heater is blowing air through the driver side air vents but is blowing cold air through the passenger side and rear console ven
ANSWER : Hi there:

Climate controlled vehicles have multiple electrical relays that open and close vents to maintain the desired temperature. In some instances, these relays can wear out overtime. However, it’s also common for debris to clog up vents (especially side vents) which may restrict the flow of cool air. The best way to determine why your AC is not working efficiently, it might be best to have a professional mechanic complete a AC inspection; so they can pinpoint the source of your issues and recommend the right repairs.

Read Full Q/A … : My heater is blowing cold air.

Air conditioning blowing mildly cold air on the coldest setting, turned off/on again, now blowing cold air, should it be checked?
ANSWER : If you are getting ready for a long trip and suspect the cooling fan may be not coming on for the radiator and a/c then you should have the a/c and cooling system performanced checked before trip. Nothing worse than breaking down when out of town in a strange area.

Read Full Q/A … : My heater is blowing cold air.

My car heater will blow hot air and drive fine for 30 minutes then my heater blows cold air and my car overheats
ANSWER : Hello. With the recent repairs that have been made to the vehicle, there is only one main heating component that you have not looked into. This would be your heater core. The heater core is responsible for pulling hot coolant from the engine. This hot coolant runs through the heater core as the ambient air is pushed through to warm before entering the cabin. If the coolant can’t flow through the heater core, then the air will blow cold. This can be caused by a clog, a faulty switch, or a process known as electrolysis (electrical current running through coolant). Unless there is a clog that can be dislodged, these issues will all result in a new heater core. To get a precise diagnosis of the problem, I recommend having an expert inspect the overheating problem so this can be resolved.

Read Full Q/A … : My heater is blowing cold air.

everytime I turn my car on the ac starts to blow air even if I switch it off. it won’t blow cold air or heat.
ANSWER : Hi there. Based on your question and input, it looks like your AC control switches are damaged, causing the vents to activate even if the switch is not activated. This is sometimes an electrical problem, as it could be triggered by a damaged electrical relay. You might want to have a professional mechanic complete an AC is not working inspection, so they can determine what is causing this issue you’re experiencing and recommend the right repair.

Read Full Q/A … : My heater is blowing cold air.

My air is blowing cold-hot-cold-hot-cold-hot…
ANSWER : It is possible that you have a leak in the AC system. There are pressure switches that will turn off the compressor if the pressure is too high or too low. The low refrigerant level could cause the AC compressor to cycle on and off. If you would like to have this done, a certified technician from YourMechanic can come to your car’s location to diagnose the AC system and make the correct repair.

Read Full Q/A … : My heater is blowing cold air.

Hot air mixed with cold blows from air conditioning
ANSWER : Hey there. You will most likely have to have a mechanic bypass the heater coolant lines to have this resolved. Your A/C may not be controlling the air flow inside the evaporator correctly out of the vents and may be the blend door actuator stuck in the heat position. Have the AC system diagnosed first before bypassing the heater.

Read Full Q/A … : My heater is blowing cold air.

My car is overheating and my heater is blowing cold air on and off
ANSWER : The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. When the cooling system is not properly circulating coolant through the motor, this results in the warm coolant not being pumped through the heater core properly in order to warm the inside of the vehicle.

Engine overheating can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. As mentioned above, this also restricts the warm coolant from flowing through the heater core which uses this to blow warm air into the cab of the vehicle. I would suggest having an expert from Your Mechanic come to your home to diagnose your cooling system.

Read Full Q/A … : My heater is blowing cold air.

While driving defroster set to hot blows hot air as it should, while idling it is blowing cold air.
ANSWER : First, the coolant level should be checked to make sure the radiator is full. While the overflow tank may be full, the radiator cap must be taken off to check the level inside the radiator. If you find the level is very low, you have a coolant leak that must be fixed. If coolant levels are normal, an engine thermostat or heater control problem may be what you’re experiencing. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at your lack of heat concern to offer a more personal diagnosis.

Read Full Q/A … : My heater is blowing cold air.