how to fix the heater not working in Toyota Highlander Third Generation (2014-2019)?

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

598 words

Problem Statement

Learn how to diagnose and fix the heater not working in Toyota Highlander 2014-2019. Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Affected Component

HVAC

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Allow the engine to cool before opening the radiator cap to prevent burns.
•Disconnect the battery before working on electrical components.

Symptoms

•No warm air blowing from the heater vents
•Cool air blowing from the heater vents regardless of temperature setting
•Fluctuating cabin temperature
•Heater control knobs/controls not responding correctly
•Warning lights related to the HVAC system illuminated on the dashboard

Diagnostic Steps

1
Check the coolant level in the radiator and overflow reservoir.
2
Inspect the cabin air filter for blockage or dirt.
3
Verify the operation of the heater control valves.
4
Use an OBD-II scanner to check for any HVAC-related error codes.
5
Test the operation of the thermostat for proper function.
6
Inspect the heater core for signs of leaks or blockages.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Ratchet and socket set
•Screwdriver set
•Pliers
•Hose clamp pliers
•Garden hose

Parts Required

•Cabin air filter
•Thermostat (if faulty)
•Heater control valve (if faulty)
•Coolant (Toyota Super Long Life Coolant)

Related Faults

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Diagnostic Steps

1
Check the coolant level in the radiator and overflow reservoir.
2
Inspect the cabin air filter for blockage or dirt.
3
Verify the operation of the heater control valves.
4
Use an OBD-II scanner to check for any HVAC-related error codes.
5
Test the operation of the thermostat for proper function.
6
Inspect the heater core for signs of leaks or blockages.

Solution

1. Preparation

Ensure the vehicle is parked on a level surface and the engine is off.
Disconnect the battery to avoid any electrical shorts during the repair.

2. Check Coolant Level

Locate the overflow reservoir and remove the cap.
Check the coolant level; if low, add the appropriate type of coolant (Toyota Super Long Life Coolant).
Start the engine and let it warm up, then check the coolant level again.

3. Replace Cabin Air Filter

Open the glove box and remove any contents.
Press the sides of the glove box to release the stops and lower it down.
Locate the cabin air filter cover and unclip it.
Remove the old filter and install a new one, ensuring it is oriented correctly.
Reassemble the glove box.

4. Inspect Heater Control Valves

Locate the heater control valves (usually near the firewall).
Check for any signs of damage or blockage.
If faulty, replace the heater control valve by disconnecting the hoses and installing a new valve.

5. Test the Thermostat

Allow the engine to reach operating temperature.
Feel the upper radiator hose; it should become hot as the thermostat opens.
If the hose remains cool, replace the thermostat by:
- Draining the coolant.
- Removing the thermostat housing.
- Replacing the thermostat and gasket, then reassemble.

6. Flush and Inspect Heater Core

If the heater core is suspected to be blocked:
- Disconnect the heater hoses from the heater core.
- Use a garden hose to flush water through the heater core until it runs clear.
- Reconnect the hoses and refill the cooling system.