Why Does My Car Heater Only Work On High? 5 Surprising Reasons!

Why does my car heater only work on high? This issue is due to a low coolant, a center not running, a machine having air, or the heater cannot work.

The primary problem may be the coolant itself that stops the heating center as it spreads hot air back to the cabin, with pollutants or rust particles in the coolant. It also suggests that the blower motor resistor is faulty; it only works on high.

Why does my car heater only work on high

The blower motor resistor fails due to a foreign object or mechanical problem in the blower motor fan blade. That avoids it as it spins freely and increases the current in the resistor, causing overheating and failure. Let us discuss more on this below. Keep reading!


Reasons Why The Car Heater Only Works On High

Here are reasons why the car heater only works on high:


#1. Low coolant

The coolant best regulates the engine temperature while the hot air flows into the cabin. The engine accumulates heat while working and collects it as heat; it transports it back to the vehicle’s radiator. The car heater works while driving only with a low coolant and a heater turned on. In this sense, a fully-functioning coolant is an answer to many vehicle components.

No heat at the idle is a sign something is wrong with it that you must check the coolant level. But then, do not open the pressurized or hot cooling system, or it might result in personal injury. Check the manual for the owner regarding checking the coolant levels. Professionally check the cooling system. There are still other reasons why the coolant is low, like the irregular leaks and maintenance in the coolant system. No matter what the cause may be, seek help from a professional technician in inspecting the issue.]


#2. Clogged heater core

The blocked heater core is also the most common car heater issue and the cause of the device working too high. The body utilizes hot engine coolant in the vehicle’s cooling system, warming up the vehicle’s cabin. The car heater issues suddenly begin to occur when the clogging begins. The pump pushes the hot coolant in the heater hose and back to a heater core.

The blower motor makes the air in the heater core fin, allowing warm air to blow through the AC ducts. The valve also opens up in some vehicles allowing the hot coolant to continue to the heater core. The coolant delivers 200 degrees and provides hot air required by the vehicle’s interior. The heater core clogged up because of debris built up, and soon, it began to malfunction with poor maintenance in the cooling system. So, get the heater core inspected by an expert because this area is challenging to access and messy to resolve. You may also be interested to know about the symptoms of a clogged heater core.


#3. Airlocked coolant system

 Air pockets also cause the heater to only work on heights that are found in the cooling system. They further prevent coolant circulation while they occur from a faulty radiator cap or low coolant. But then, the low coolant levels lead to overheating, poor engine performance, and inconsistency in heat and cold air from the cabin vents.


#4. Thermostat stuck opened

The vehicle’s thermostat maintains the accurate engine temperature and controls the coolant flow from an engine. Corrosion and debris build-up prevent it from sudden closing. When the component stays open, you experience a low temperature in the machine. When the engine does not warm up correctly, it is associated with a stuck and available thermostat. The heater does not put the warmth together as needed. The car’s heater stops blowing hot air, or it gets idle.


#5. Car is not warmed

Why does my car heater only work on high? It only works on high and does not blow out heat correctly because the car is not warmed. But you will not do this if the vehicle is warm as it blows heat and cools after 15 to 20 minutes, as this is normal, with the internal sensor reaching a specific set point. For example, you may have set it at around 80 as the car interior goes 80, and it suddenly blows a little cooler air or at least hot air. If it’s 80 in the interior and you turn it to 85 dials, you should feel the hot air already come out. As it reaches 85, the cooler air blows out and maintains the temperature. The interior is so warm that the sensor realizes it no longer needs to blow hot air with the set temperature it is put in.


It’s A Wrap!

Now you learn the answer, “why does my car heater only work on high?” Because the car is not warmed, the thermostat is stuck open, the coolant system is airlocked, the heater core is clogged, and the low coolant is. Once the issues arise, they can signal that the car heater only works on high. So, please share this information to help others with their car heater and solve the problem right away. You may also want to read about what is the best portable car heater and how to make your car heater hotter.

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