what should I check if my Honda Accord heater only blows cold air

Honda Accord 9th Generation (2013-2017)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

576 words

Problem Statement

Learn how to diagnose and fix a Honda Accord heater that blows cold air. Step-by-step guide with diagnostic procedures 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 coolant system.
•Wear safety glasses and gloves.

Symptoms

•Heater only blows cold air
•Temperature gauge reading lower than normal
•Coolant leaks under the vehicle
•Foggy windows due to inadequate defrosting
•No change in air temperature when adjusting the heater controls

Diagnostic Steps

1
Check Coolant Level: Inspect the coolant reservoir and radiator for proper coolant levels.
2
Inspect for Leaks: Look for any signs of coolant leaks around hoses, the radiator, and the engine block.
3
Test Thermostat Function: Verify that the thermostat opens at the correct temperature by checking engine temperature during operation.
4
Check Heater Core: Measure the temperature of the hoses leading to and from the heater core to determine if hot coolant is passing through.
5
Examine Heater Control Valve: Ensure that the heater control valve is functioning and allowing coolant to flow into the heater core.
6
Scan for Error Codes: Use an OBD-II scanner to check for any relevant diagnostic trouble codes (DTCs) related to the heating system.

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

•Socket set
•Pliers
•Coolant pressure tester
•OBD-II scanner

Parts Required

•Thermostat (if faulty)
•Coolant
•Heater control valve (if malfunctioning)
•Heater core (if clogged)

Related Faults

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Diagnostic Steps

1
Check Coolant Level: Inspect the coolant reservoir and radiator for proper coolant levels.
2
Inspect for Leaks: Look for any signs of coolant leaks around hoses, the radiator, and the engine block.
3
Test Thermostat Function: Verify that the thermostat opens at the correct temperature by checking engine temperature during operation.
4
Check Heater Core: Measure the temperature of the hoses leading to and from the heater core to determine if hot coolant is passing through.
5
Examine Heater Control Valve: Ensure that the heater control valve is functioning and allowing coolant to flow into the heater core.
6
Scan for Error Codes: Use an OBD-II scanner to check for any relevant diagnostic trouble codes (DTCs) related to the heating system.

Solution

1. Preparation

Tools Required: Socket set, pliers, coolant pressure tester
Safety Warnings: Allow the engine to cool before opening the coolant system. Wear safety glasses and gloves.

2. Check and Refill Coolant

Sub-steps:
1. Locate the coolant reservoir and radiator cap.
2. Remove the radiator cap (when cool) and check the coolant level.
3. If low, mix the appropriate coolant with water based on manufacturer specifications and refill to the proper level.

3. Inspect and Repair Leaks

Sub-steps:
1. Visually inspect the radiator, hoses, and water pump for leaks.
2. If leaks are found, replace damaged hoses or components as necessary.

4. Replace Thermostat (if faulty)

Sub-steps:
1. Drain the engine coolant into a clean container.
2. Disconnect the thermostat housing and remove the old thermostat.
3. Install the new thermostat in the correct orientation.
4. Reattach the thermostat housing and refill coolant.

5. Flush and Replace Heater Core (if clogged)

Sub-steps:
1. Disconnect the heater core hoses from the engine.
2. Use a garden hose to flush the heater core in both directions until clear water flows.
3. Reconnect hoses and refill coolant.

6. Verify Heater Control Valve Operation

Sub-steps:
1. Locate the heater control valve and ensure it’s connected to the heater control system.
2. Manually check the valve operation; replace if it’s stuck or malfunctioning.