Two people working on truck engine

How Do You Know If Your A/C Compressor is Bad? Signs and Symptoms

No matter where you usually drive, you want your truck to have air conditioning that works well and works quickly. The A/C system in your truck has a long list of parts, however, and a failure of any one of them can mean a hot and uncomfortable cab. While some failures may happen suddenly, there are others that will give you plenty of notice before they stop working. We’re going to take a look at the most common signals that your A/C compressor is going, or has gone, bad.


What Is An AC Compressor And What Does It Do?

The compressor is the primary pump of the air conditioning system. It is a belt-driven accessory that has a clutch to determine when the compressor receives power from the engine. When the A/C is off, the clutch is disengaged, and the pulley spins freely and simply acts as an idler pulley.

When the clutch engages, however, the compressor begins operating and increasing the pressure of the refrigerant in the system. This higher-pressure refrigerant is then pumped to the evaporator and condenser, where the heat is exchanged and the blower motor blows air across the cooling coils or lines.


What Can Cause A Bad AC Compressor?

There are several things that can cause your A/C compressor to go bad. One of the most common is a leak in the system somewhere that causes low refrigerant levels. Since the refrigerant acts as the lubricant for the compressor, this can cause overheating, bearing failure and more.

Additional ways your compressor can be damaged include:

  • Electrical issues, such as overvoltage
  • Blocked condenser coils
  • Blocked suction lines
  • Cracked or displaced evaporator motor
  • Overfilled refrigerant


Signs & Symptoms of a Bad AC Compressor

While this list is definitely not exhaustive, it does list the most common signs that the compressor is going out on your air conditioning system. There are associated failures that may happen as well, depending on the circumstances, and we’ll get into those later.

No Cold Air

Turning on the air conditioning and not feeling any cold air, or worse, feeling hot air, is one of the most obvious and disappointing signs that your compressor may be bad. While this may sound like common sense, if there is no cold air coming out there are a few other things that you should keep an eye out for, which may indicate the failure belongs to the compressor.

To try and narrow down the possibilities a bit, make sure that the A/C is on, indicated by a light, an icon or other indicators. You can also test the voltage of the wire that connects to the compressor to see if the compressor is getting power. This may sound invasive, but there are tools that allow you to test for current with induction.

Compressor Noise

Just like with many other problems under the hood of your truck, a failing compressor or one that has already died is likely to signal this by making noises. The most common noise will be a high-pitched metallic sound or grinding noise that indicates the bearings on the compressor pulley are going bad.

If you suspect your A/C compressor is making noise, it can be relatively easy to troubleshoot. While stopped, open your window and turn the A/C on, then off. If you notice a change in the noise, it is likely the compressor. Otherwise, the noise may be from another engine accessory.

No Clutch Movement

All belt-driven A/C compressors will have a clutch as a method of disengaging the compressor from the engine. The inner portion of the pulley will spin even when the compressor is not running, but the outer portion is the clutch that will allow the compressor to draw engine power. If you turn the A/C on and there’s no movement from the clutch, that could be the issue.

The biggest problem, however, is that the clutch cannot be serviced separately, like in other cases. If the clutch goes bad, the entire compressor will need to be replaced. In some cases where the clutch is stuck in the engaged position, you may be able to route your belt around the A/C compressor until you can get it serviced.

Smell of Burning Rubber

An indication that your A/C compressor just went bad, likely during use, is having a sudden smell of burning rubber in the cab. This smell will often be accompanied by smoke from the engine bay and, if not stopped quickly enough, the loss of the belt.

This is what happens when either the compressor or the compressor pulley seizes during operation. The resulting stopped pulley, combined with the belt still being spun by the engine, creates an incredible amount of friction on the pulley, and that can cause the belt to burn. If the heat becomes intense enough, the belt can melt and fail entirely.

Added Wearing of the Auxiliary Drive Belt

Having the need to replace your auxiliary drive belt more frequently due to increased wear can be one of the ways that you can tell if your A/C compressor is going bad. It is also one of the ways that provide the most lead time to failure.

If the compressor pulley is beginning to fail, it will rotate slightly unevenly, which can cause the belt to shimmy and grab on the auxiliary drive belt. This can cause wear to the edges of the belt, and it may even be accompanied by significant squealing. Another cause of this can be belts that are not tensioned correctly.

Loss of Refrigerant

One of the little-known causes of compressor failure is actually more of a fail-safe, and it’s the low-pressure switch. The switch is connected to a sensor that determines when the refrigerant level in the system has dropped below the minimum required to operate the compressor safely.

In many cases, the loss of refrigerant is due to a previously undetected leak. The leak can be simple to troubleshoot and find, but if it is a result of the compressor being damaged, or because the bearings have worn aEvery ACnd lost their seal, it cannot be repaired and the compressor must be replaced. If the leak is in a refrigerant line, it can generally be repaired easily.

Additional A/C Components Prone to Failure

Sometimes, the failure isn’t the compressor, and instead is something much easier and cheaper to fix. Here are some ideas of items to check:


Your A/C system will often have its own fuse, or more than one, and if they are blown, it can be a simple fix. Be sure to look into what blew the fuse in the first place, however.


Since your compressor is powered by a drive belt, be sure that the belt is properly installed and tensioned. Too loose and it won’t drive the compressor; too tight and it can contribute to premature wear of component pulleys.

Air Filter

Sometimes it only feels like your AC isn’t working, because the cold air can’t get to you. Check your cabin air filter and make sure your air conditioning can breathe.

Blower Motor

The blower motor is another reason that you may not feel cold air, even when the system is working. If the blower isn’t moving warm air across the refrigerated coils hard enough to make it to the cabin, you aren’t going to feel that A/C.


How to Diagnose a Bad AC Compressor

There are several ways to determine for sure if your compressor is bad. You can check the voltage going to the compressor, and you can check to see if it’s engaging and pumping as needed. The problem is that there are other things that may be preventing the compressor from engaging or running properly.

If you think that your A/C compressor may be bad, the best way to determine for sure if that is the problem is to take it to a qualified local shop, like Blaine Brothers. We’ll make sure that the problem is diagnosed correctly, and that the fix is performed by the book, so you don’t have to worry about any issues down the road.


How to Fix an AC Compressor

While you can order an A/C compressor for your truck from just about any common parts supplier, the process of installing it requires trained experts that are familiar with the process and the potential problems that can happen in the process.

The best way to make sure your A/C compressor is fixed the right way, the first time, is to take your truck to Blaine Brothers. Not only do we have the knowledge and skills to install your compressor correctly, but we’ll also make sure you get honest pricing and guaranteed service


Stop By and Get A Fix or Replacement AC Unit Today!

If you’re hitting that A/C button and you aren’t feeling frosty relief, it may be time to have a professional take a look at your compressor. The trusted experts at Blaine Brothers can get your A/C problems diagnosed and fixed quickly, so you’re back on the road. Contact us today for more information!

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