What is an AC compressor relay?
An AC compressor relay is an electric switch that controls the operation of your car’s AC compressor. It serves as a bridge between your AC controls and the compressor, allowing an electrical signal to activate the compressor when you turn on the AC system. This setup enables you to control the temperature settings and airflow from inside the cabin.
When should I replace the AC compressor relay on my car?
There isn’t a fixed replacement schedule for the AC compressor relay. Instead, you only need to replace it when it fails. Here are the most common signs of AC compressor relay failure:
Inconsistent cooling: If the relay is failing, your compressor may turn on sometimes but not other times. You may notice weak or inconsistent airflow.
The compressor doesn’t turn on: Normally, when you turn on your car’s AC system, you can hear the compressor kick into gear and activate. If the relay is bad, the compressor won’t start, and you won’t hear the compressor clutch engage.
AC system failure: If the AC compressor relay is bad, the HVAC system won’t be able to cool your car’s cabin. You’ll likely notice that hot air flows from the vents in this case.
Keep in mind: These issues can indicate other problems with your car’s AC unit, including a refrigerant leak, bad evaporator, faulty expansion valve, or even clogged cabin air filter. The best way to accurately diagnose the problem is to contact a mechanic.
How often should I replace my AC compressor relay?
There are no fixed intervals for replacing the AC compressor relay, but the part is subject to wear and tear and will likely fail over time. You should replace your ac compressor relay when it stops working correctly.
The most common signs of AC compressor relay failure include warm air from the AC system and intermittent cooling.
Can I replace my AC compressor relay myself?
Yes—an AC compressor relay replacement is an excellent DIY project. It requires minimal automotive experience and no special tools.
You can use your vehicle owner’s manual
or a repair guide to identify the location of the relay—from there, it’s as simple as pulling the old one out and plugging in the new one. All that said, if you’re uncomfortable performing the repair yourself, you should contact a professional mechanic to help you.