Why is there no heat in my Subaru Forester?

No heat in a Subaru Forester is usually caused by a heating-system issue such as low coolant, a faulty thermostat, a blocked or leaking heater core, or a malfunctioning heater blend door or valve.

In simple terms, cabin warmth requires hot engine coolant to reach the heater core and for the HVAC system to channel that warmth into the interior. If any part of that chain fails—coolant flow, a valve, a blend door, or the climate-control controls—the air your fans push into the cabin will stay cool.

Common causes of no heat in a Subaru Forester

These are the most frequent culprits when a Forester won’t produce warm air.

• Low coolant level or coolant leaks


• Air in the cooling system or incomplete bleeding


• Thermostat stuck open (engine runs cooler than normal)


• Heater core is clogged or leaking


• Heater control valve stuck closed (in models that use a valve)


• Blender door or actuator failure (controls hot vs. cold air)



• Blocked or damaged heater hoses or weak water pump affecting coolant flow

Most heat-loss conditions hinge on coolant circulation and the path that warm air takes into the cabin. A systematic check can help identify the exact failure point.

Diagnostic steps you can take

To systematically check the issue, follow this practical, step-by-step guide.

1. Confirm coolant level: with the engine cold, inspect the reservoir and the overflow bottle. Top up with the correct mix if low, and inspect for leaks around hoses, radiator, and the radiator cap.


2. Look for signs of leaks or damp carpeting: a heater-core leak can leave a sweet coolant smell and damp carpet on the passenger side floor.


3. Check engine temperature behavior: start the car and set heat to maximum with the fan on. If the engine stays cool or takes a long time to reach operating temperature, the thermostat may be stuck open.


4. Feel the heater hoses at the firewall: with the engine up to temp, the hose feeding the heater core should get hot. If one hose is hot and the other remains cool, there may be a restriction, valve issue, or a blend-door problem.


5. Test the heater valve or blend door: in cars with a heater control valve, switching between hot and cold should change the flow of hot coolant. Listen for distinct changes in the HVAC behavior when you adjust the temperature; a non-responsive system can indicate a faulty valve or stuck blend door actuator.


6. Assess the climate-control system: if the fan runs normally but you can’t vary heat output, or you hear strange noises when changing temperature, a control module or actuator fault could be present.


7. Consider flushing or inspecting the heater core: if you’ve ruled out coolant and valve issues, a professional may flush the core or replace it if clogged or leaking.

If any of these steps indicate a deeper issue, or you notice coolant odor, persistent leaks, or overheating, seek professional service promptly.

When to seek professional help

Call a mechanic if you observe any of the following: persistent coolant leaks, damp carpets with a sweet odor, overheating, or if the steps above do not restore heat after topping up coolant or replacing a faulty part. A certified technician can perform deeper diagnostics, including pressure tests, heater-core flow checks, and electrical tests for the HVAC system.

Preventive maintenance and quick checks

Regular maintenance can reduce the likelihood of heat-related issues in your Forester. Consider these preventive steps.

• Regularly check and maintain coolant level and quality; follow Subaru’s recommended interval for coolant replacement.


• Inspect hoses for cracks, swelling, or leaks and replace damaged hoses promptly.


• Bleed the cooling system after draining or replacing coolant to remove air pockets that can impair heater performance.


• Keep the heater core and related components clean and free from debris; if you notice decreased heat, consider a professional heater-core flush.


• If your vehicle has a heater control valve or blend-door actuator, have them tested during routine service, especially if you notice delayed heat or temperature swings.

Summary

No heat in a Subaru Forester almost always points to a cooling-system or HVAC-control issue—often low coolant, air in the system, a thermostat problem, a clogged heater core, or a faulty valve or blend door. Start with simple checks (coolant level, signs of leaks, heater-hose temperatures) and progress to more involved diagnostics or professional service if the heat still won’t return. Keeping up with regular coolant maintenance and HVAC checks can help prevent heat-loss problems in the future.

Why is my Subaru heater not blowing hot air?

A Subaru's heater not blowing hot air is often caused by a low or dirty coolant level, a thermostat stuck open, or a clogged heater core. Other common issues include a faulty blower motor or resistor, which would affect fan speed, or a problem with the blend door, which directs airflow. 
Common causes and solutions
Cooling system problems 

• Low or dirty coolant: Insufficient coolant can prevent the heater core from getting hot. 
  • Solution: Check and top off coolant, and if it's dirty, have the system flushed and refilled. 
• Stuck-open thermostat: The thermostat regulates engine temperature. If it's stuck open, the engine won't warm up enough for the heater to produce heat. 
  • Solution: Replace the thermostat. 
• Clogged heater core: Debris can block the small passages in the heater core, preventing hot coolant from flowing through it. 
  • Solution: Try flushing the cooling system or back-flushing the heater core. If that fails, it may need replacement. 
• Air trapped in the system: Air pockets can block coolant flow. 
  • Solution: Bleed the air from the cooling system. 
• Faulty water pump: If the pump isn't circulating coolant effectively, the heater will not get hot. 
  • Solution: The water pump may need to be replaced. 

Airflow problems

• Faulty blower motor: A bad motor can result in weak or no airflow from the vents. 
• Faulty blower motor resistor: This component controls fan speed. If it fails, the fan may only work on certain speeds or not at all. 
• Faulty blend door or actuator: The blend door controls whether air flows through the heater core or the AC evaporator. If the door is stuck in the "cold" position or the actuator that controls it has failed, you will only get cold air. 
  • Solution: You may hear a clicking or knocking sound from the dashboard if the actuator is failing. A professional can diagnose and replace the faulty component. 

Quick diagnostic steps
This video explains how to diagnose no heat issues in your car: 54s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Oct 19, 2022

1. Check coolant: Ensure the engine is cool, then check the coolant level in the reservoir and radiator. 
2. Feel heater hoses: Locate the two heater hoses going into the firewall under the hood. With the engine warm and the heater on high, touch both hoses. Both should feel hot. If one is significantly cooler, you likely have a clogged heater core. 
3. Inspect blend door: Turn the temperature from full hot to full cold and listen for any clicking or knocking sounds coming from the dashboard. 
4. Test blower motor: Check if the fan speed changes correctly with the control dial. If it only works on high, the resistor is likely bad. 

What is the most common problem with the Subaru Forester?

The most common problem with the Subaru Forester is the continuously variable transmission (CVT), which can suffer from issues like shuddering, delayed acceleration, and whining noises, and may require expensive repairs. Other frequent issues include problems with the engine (especially oil consumption), the electrical system, and, in certain model years, issues with windshields cracking and batteries dying quickly.
 
You can watch this video to learn more about Subaru Forester common problems: 51scar PROblemsYouTube · Feb 19, 2024
Transmission (CVT)

• Shuddering and jerking: This often occurs when accelerating from a stop.
• Delayed acceleration and slipping: The engine revs up but the car doesn't speed up as expected, which can be dangerous when merging.
• High-pitched whining: This can be a sign of worn pulley bearings inside the transmission.
• Repair cost: CVTs are often not rebuildable and require a complete, expensive replacement. 

Engine

• Excessive oil consumption: Many model years, particularly from the 2014-2018 generation, are known for burning through oil rapidly.
• Oil leaks: Leaks, often requiring expensive engine replacements, are another reported problem. 

Electrical and other issues

• Electrical malfunctions: Issues can range from infotainment system glitches and GPS errors to more serious problems like a battery dying prematurely or the EyeSight safety system turning off unexpectedly. 
• Air conditioning (AC): Some models experience AC failure that can be costly to fix. 
• Windshields: In the 2019-2024 generation, windshields can crack from small chips. 
• Airbag malfunctions: Older models, such as the 2009-2011, have been associated with malfunctioning airbags. 

This video explains some of the most common issues with the Subaru Forester, including the transmission and engine: 57sGear GazetteYouTube · Oct 23, 2025

Why is my air working but not my heat in my car?

Low Coolant Levels
The heating system in your car relies on the hot coolant that circulates through the engine. If you notice your car heat not blowing hot air, low coolant levels might be the culprit. If your coolant levels are low, there might not be enough to heat up and warm your car.

Why is my car blowing out cold air when the heat is on?

Your car is likely blowing cold air when the heat is on because of a low coolant level, a faulty thermostat, a clogged or broken heater core, or an airlock in the cooling system. Other possible causes include a bad blower motor, a clogged cabin air filter, or malfunctioning heating controls. To diagnose the problem, first check the coolant level and listen for the engine to reach its normal operating temperature. 
You can watch this video to learn about the symptoms of a clogged or leaky heater core: 49sTop 5 Auto RepairsYouTube · Sep 14, 2023
Common causes

• Low coolant level: Coolant transfers heat from the engine to the heater core. If the level is too low, there isn't enough heat to warm the air. This is often caused by a leak in a hose, the radiator, or the water pump. 
• Faulty thermostat: The thermostat regulates the flow of coolant. If it's stuck closed, coolant can't circulate to the heater core to provide heat. 
• Clogged or damaged heater core: The heater core is a small radiator that heats the air. Over time, it can become clogged with debris or rust, preventing hot coolant from flowing through it properly. 
• Airlock in the cooling system: Air bubbles can get trapped in the cooling system, blocking the flow of coolant to the heater core. This can be fixed by bleeding the air from the system. 
• Malfunctioning heating controls: The cables or electronic components that control the blend door (which directs air over the heater core) or the temperature can break or become stuck. 

What to check and do

1. Check engine temperature: When the engine has been running for a while, check if the temperature gauge is in the normal range. If it's still on "cold," the thermostat is a likely culprit. 
2. Check coolant level: Look at the coolant reservoir. If the level is low, top it off with the correct mixture of coolant and water. Check for any signs of a leak, such as puddles under the car. 
3. Check for blockages: If coolant levels are normal, a blockage is likely. You can try a cooling system flush, or a mechanic can check for blockages in the heater core itself. 
4. Inspect heating controls: Check the vents and controls for any signs of damage or sticking. You may need to have them repaired or replaced. 

This video explains the steps to troubleshoot a car heater blowing cold air: 1:06Dannys DIY GarageYouTube · Oct 22, 2025