how to fix the rear AC not blowing cold air in my Toyota Highlander Third Generation (2014-2019)?

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

4 min read

670 words

Problem Statement

Learn how to diagnose and fix the rear AC not blowing cold air in a Toyota Highlander (2014-2019). Step-by-step guide with symptoms and solutions.

Affected Component

HVAC

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening the AC system to avoid burns.

Symptoms

•Rear air conditioning vents blowing warm air
•Inconsistent temperature between front and rear AC
•Unusual noises coming from the rear AC unit
•Condensation or water pooling near the rear AC vents
•Warning lights related to the AC system may be illuminated on the dashboard

Diagnostic Steps

1
Check the refrigerant level in the AC system using a manifold gauge set.
2
Inspect the rear AC blower motor for functionality.
3
Verify the operation of the rear AC control module and temperature settings.
4
Look for any visible leaks in the refrigerant lines or around the rear AC unit.
5
Test the rear evaporator temperature with a thermometer.
6
Scan for any error codes using an OBD-II scanner specific to the HVAC 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

•Manifold gauge set
•Screwdriver set
•Multimeter
•OBD-II scanner
•Refrigerant recovery machine

Parts Required

•Refrigerant (R-134a)
•Blower motor (if faulty)
•Rear evaporator (if required)

Related Faults

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Diagnostic Steps

1
Check the refrigerant level in the AC system using a manifold gauge set.
2
Inspect the rear AC blower motor for functionality.
3
Verify the operation of the rear AC control module and temperature settings.
4
Look for any visible leaks in the refrigerant lines or around the rear AC unit.
5
Test the rear evaporator temperature with a thermometer.
6
Scan for any error codes using an OBD-II scanner specific to the HVAC system.

Solution

1. Preparation

Gather all necessary tools and parts.
Disconnect the vehicle battery to ensure safety.
Allow the vehicle to cool down if it has been running.

2. Check Refrigerant Level

Tools Required: Manifold gauge set
Connect the manifold gauges to the low and high-pressure service ports of the AC system.
Read the pressure levels; they should be within the manufacturer's specifications (typically 30-40 PSI on the low side and 200-250 PSI on the high side).
If levels are low, proceed to recharge the system with the appropriate refrigerant.

3. Inspect Rear AC Blower Motor

Tools Required: Screwdriver set, multimeter
Remove the access panel to the rear AC unit.
Use a multimeter to test the blower motor for continuity; if there is no continuity, replace the blower motor.
If the blower motor is operational, check the fan speed settings and wiring connections.

4. Examine the Rear AC Control Module

Tools Required: OBD-II scanner, wiring harness tester
Use an OBD-II scanner to check for any fault codes related to the rear AC.
Inspect wiring connections to the rear AC control module for any loose or damaged wiring.
Reset any codes and test the rear AC operation again.

5. Inspect for Leaks

Tools Required: UV leak detection kit (optional)
Visually inspect all refrigerant lines for signs of leaks, such as oil residue.
Use a UV light and dye if necessary to track down any subtle leaks in the system.
Repair or replace any damaged lines or components.

6. Replace Rear Evaporator (if necessary)

If the rear evaporator is found to be blocked or damaged, it will need to be replaced.
Tools Required: Socket set, screwdrivers, refrigerant recovery machine
Recover the refrigerant from the system using a recovery machine.
Remove the rear AC unit, including the evaporator, and replace it with a new one.
Reassemble all components and recharge the AC system.