Subaru Ac Blows Cold Then Warm

Introduction

Is your Subaru’s air conditioning blowing cold air intermittently, only to be followed by warm air at the most inconvenient times? This frustrating issue is a common problem for many car owners. It not only makes driving uncomfortable, especially during hot weather, but it can also indicate an underlying problem that, if left unaddressed, could lead to more costly repairs down the road. Addressing this issue promptly will save you from unnecessary discomfort and potential financial burdens.

Common Causes of Subaru AC Blows Cold Then Warm

Here are some of the most frequent culprits behind your Subaru’s inconsistent AC performance:

Low Refrigerant: This is the most common cause. Like the coolant in your engine, your AC system relies on refrigerant to cool the air. If the level is low due to a leak, the system may cycle between cold and warm.
Faulty Compressor Clutch: The compressor clutch engages and disengages the AC compressor. If it’s failing, the compressor may not run consistently, leading to intermittent cooling.
Blocked Condenser: The condenser dissipates heat from the refrigerant. If it’s blocked by debris (leaves, bugs), it can’t do its job effectively, causing the AC to blow warm air.
Failing Expansion Valve: The expansion valve regulates the flow of refrigerant into the evaporator. A malfunctioning valve can cause inconsistent refrigerant flow, leading to fluctuating temperatures.
Electrical Problems: Issues with wiring, relays, or sensors in the AC system can cause the compressor to turn on and off sporadically.
Overcharged Refrigerant: While low refrigerant is a common problem, too much refrigerant can also cause issues. Overcharging can prevent the system from functioning properly.
Vacuum Leaks: Vacuum leaks in the system can cause the blend door to malfunction. The blend door mixes hot and cold air.
Bad Cabin Air Filter: Although it sounds counter-intuitive, a very dirty cabin air filter can restrict air flow. It can also cause freezing up in the system, leading to inconsistent temperatures.

Symptoms Checklist

Look for these indicators to help pinpoint the problem:

AC blows cold for a few minutes, then warm.
AC works fine at highway speeds, but warms up in city traffic.
AC makes unusual noises, such as clicking or hissing.
Engine overheating along with AC issues.
Reduced airflow from the vents.
Visible leaks or oily residue near AC components under the hood.

How to Fix Subaru AC Blows Cold Then Warm Step-by-Step Guide

Follow these steps to troubleshoot your Subaru’s AC:

Visual Inspection: Start by looking for obvious signs of damage, such as leaks or broken components around the AC compressor, condenser, and refrigerant lines.
Check the Cabin Air Filter: Locate the cabin air filter (usually behind the glove box) and inspect it. A clogged filter restricts airflow and can cause freezing. Replace it if dirty.
Clean the Condenser: The condenser is located in front of the radiator. Gently clean it with a soft brush and a hose to remove any debris. Be careful not to damage the fins.
Check the Compressor Clutch: With the engine running and AC on, observe the compressor clutch. It should engage (spin) and disengage (stop) periodically. If it’s not engaging at all, or engaging erratically, there may be a problem with the clutch or the compressor itself.
Listen for Unusual Noises: Listen closely for any unusual noises coming from the AC compressor. Grinding, squealing, or rattling noises can indicate a failing compressor.
Test the Blower Motor: Make sure the blower motor is working correctly on all speed settings. If the blower motor is not working, you may not be getting any airflow at all.
Check the Fuses and Relays: Consult your owner’s manual to locate the fuses and relays for the AC system. Check them for damage or corrosion. Replace any blown fuses.
Inspect Refrigerant Lines: Inspect the refrigerant lines for any signs of damage or leaks. Look for oily residue around fittings and connections.
Check the Blend Door Actuator: The blend door mixes hot and cold air. Try adjusting the temperature setting from hot to cold. Listen for the blend door actuator moving behind the dashboard. If you dont hear it or it sounds erratic, it might be failing.
Battery Voltage: Ensure the battery voltage is adequate as a low voltage could affect the compressor clutch engagement.

Fix the Issue Without Buying Parts

Here are some things to try that don’t involve purchasing new parts:

Cleaning: As mentioned before, thoroughly clean the condenser and replace the cabin air filter.
Fuse Reset: Remove the AC fuse for 10 minutes and then put it back in. This can sometimes reset the system and clear minor glitches.
Visual Inspection: Carefully inspect all AC lines, connections, and components for any obvious signs of damage or leaks. Catching a small leak early can prevent bigger problems later.
Ensure No Obstructions: Check the outside vents of your AC system for any blockage. Sometimes debris or leaves can become lodged and reduce the efficiency of the cooling system.

When Replacement Might Be Necessary

If the above steps don’t resolve the issue, you may need to consider replacing some parts. The compressor is often the culprit, and that can be expensive. A compressor replacement, including labor, could cost between $600 and $1200. Other parts that commonly fail are the condenser ($300-$700), expansion valve ($150-$400), and compressor clutch ($200-$500). Getting a professional diagnosis before replacing any parts is essential.

Safety Warning

Always disconnect the negative battery cable before working on any electrical components.
Refrigerant can be harmful. Avoid contact with skin and eyes. If you suspect a refrigerant leak, consult a professional.
Wear safety glasses when working under the hood.
Never attempt to open or repair the AC compressor yourself. This requires specialized equipment and training.

Tools You May Need

Screwdrivers (Phillips and flathead)
Wrench set
Socket set
Pliers
Multimeter (for testing electrical components)
Soft brush (for cleaning the condenser)
Safety Glasses
Gloves

FAQ

Q: Why does my AC blow cold at high speeds but warm at low speeds?
A: This is often due to insufficient airflow over the condenser at low speeds. Cleaning the condenser or checking the cooling fan can help.

Q: Can I recharge the AC myself?
A: While DIY refrigerant recharge kits are available, it’s generally not recommended unless you have experience and the proper tools. Overcharging or using the wrong type of refrigerant can damage the system.

Q: How often should I have my AC system serviced?
A: It’s a good idea to have your AC system inspected at least once a year, especially before the start of summer. A professional can check the refrigerant level, inspect the components, and identify any potential problems.

Q: My car is making a hissing noise when I turn on the AC. What could that be?
A: A hissing noise often indicates a refrigerant leak. Have the system inspected by a professional as soon as possible.

Conclusion

Troubleshooting your Subaru’s AC issue can be a rewarding DIY experience. By following these steps, you can identify and potentially resolve the problem yourself. However, if you’re not comfortable working on your car’s AC system or if the problem persists, it’s always best to consult a qualified technician. Getting a professional diagnosis and repair will ensure your AC system is functioning properly and keep you cool on the road. Don’t hesitate to get your system looked at it could save you money and discomfort in the long run!