how to fix AC compressor not engaging 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

548 words

Problem Statement

Learn how to diagnose and fix the AC compressor not engaging in a 2014-2019 Toyota Highlander. 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

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

Symptoms

•AC compressor clutch not engaging
•Warm air blowing from vents
•AC system not cooling
•Possible check engine light illuminated
•Unusual noises from the engine bay when AC is attempted to be engaged

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to check for any related trouble codes.
2
Inspect the AC fuse and relay to ensure they are functioning properly.
3
Check the refrigerant level to confirm it is within the operating range.
4
Measure voltage at the AC compressor connector while the AC is turned on to verify electrical supply.
5
Inspect the AC compressor and associated wiring for any signs of damage or wear.
6
Test the AC pressure switch to ensure it is functioning correctly.

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
•Multimeter
•Refrigerant gauge set
•Socket set
•Torque wrench

Parts Required

•AC fuse (if blown)
•AC relay (if defective)
•Refrigerant (R-134a)
•AC compressor (if necessary)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to check for any related trouble codes.
2
Inspect the AC fuse and relay to ensure they are functioning properly.
3
Check the refrigerant level to confirm it is within the operating range.
4
Measure voltage at the AC compressor connector while the AC is turned on to verify electrical supply.
5
Inspect the AC compressor and associated wiring for any signs of damage or wear.
6
Test the AC pressure switch to ensure it is functioning correctly.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the vehicle's battery to ensure safety while working on electrical components.

2. Inspect and Replace Fuses

Locate the fuse box, usually under the dashboard or in the engine bay.
Check the AC fuse for continuity using a multimeter.
If blown, replace with a fuse of the same amperage.

3. Replace AC Relay

Locate the AC relay in the fuse box.
Remove the relay and test it with a multimeter.
If defective, replace with a new relay.

4. Recharge Refrigerant

Connect a refrigerant gauge set to the AC service ports.
Check the low and high-side pressures to determine if the system is low on refrigerant.
If low, add the appropriate type and amount of refrigerant (typically R-134a for this generation).
Monitor the system while recharging to prevent overcharging.

5. Repair or Replace AC Compressor

If the compressor is not engaging after checking the electrical supply:
- Remove the drive belt from the AC compressor.
- Disconnect the electrical connector from the AC compressor.
- Remove the mounting bolts and take out the compressor.
- Install the new or refurbished compressor, ensuring to replace any O-rings and seals.
- Reconnect the electrical connector and reattach the drive belt.

6. System Test

Reconnect the vehicle's battery.
Start the engine and turn on the AC to check if the compressor engages.
Verify that cold air is blowing from the vents.