How to Troubleshoot the A/C in Your Truck

Truck drivers rely on their air conditioning not only for comfort while driving but for safety as well, both on and off the road. One of the most frustrating things is when you’re driving through a hotter area and suddenly your system goes from blowing icy cold air to blowing warm air, or even no air at all. This is a prime indication that something is going on with your A/C system in your truck.

We’re going to look at what components make up your truck’s air conditioning system, and how they contribute to the frosty miracle. Then, we’ll look at common problems, how you can use them to help determine what components may have failed, and how you can test those components. In the end, if you need professional help, we’ll be able to provide guidance on that as well.


How To Troubleshoot Your A/C

The air conditioning system in your truck is a highly complex system of gas and thermal exchange. However, since all of the components have a very specific function that yields a very specific result, it is possible to figure out what may be wrong before taking the truck to a shop to pay for a diagnosis.

Troubleshooting your truck’s A/C problem will require you to start with the symptom that is being experienced and use this symptom in combination with other signs to determine which component is most likely to have failed. In some cases, there are also tests that can be done to reduce the chance of error.


Key Components of Your Vehicle’s A/C

These components are the primary components of your truck’s A/C system:


The refrigerant that is pumped into your truck’s air conditioning is a special gas that has the unique ability to change its attributes when compressed. There are many types of refrigerant that have been used through the years, but the most recent version and current industry standard refrigerant is R-135a.


The compressor is responsible for compressing the refrigerant gas into a liquid again. It compresses the refrigerant into a high-pressure gas, which also adds a significant amount of heat to the system. Once the gas has been compressed it is sent to the condenser.


The condenser takes the pressurized and heated gas and cools it into a liquid. This is generally done with a series of coils that allow cooler air to remove the heat from the outside to cool the coils. This cools the gas and reverts it to a liquid state, which allows it to operate much more efficiently.


The drier, also sometimes called the accumulator, or the filter-drier is a canister that is loaded with a special desiccant to pull moisture out of the air. Sometimes these will also have a small sight glass on them so that the system’s flow can be observed. The drier is the part of the system that makes the cool air into dry air.


The evaporator allows the misted refrigerant to flow through cold tubes, where the blower motor blows air across to create cold air. That cold air is directed into the cab of the truck to make it more comfortable.


Diagnosing Common AC Issues

Now that we’ve identified the primary components of the system, we’re ready to start troubleshooting and looking for clues regarding the failed air conditioning operation. Here are some of the most common problems, as well as the solutions to those problems:

Cool, But Not Cold, Air

If you turn on your A/C, set it to the maximum with the fan blowing hard, and are only feeling moderate amounts of cool air, it may be a problem related to the condenser or airflow.

First, start your truck and turn the A/C on, and look for any signs of the fans not working. Then assess the condition of the condenser. Sometimes they can accumulate sticks, leaves, bugs and dirt that can keep them from operating optimally. If anything is found, ensure that it’s cleaned off.

Another potential issue is that the air filter for the cabin is too dirty to allow for free airflow. This is usually less likely because most drivers keep their cabin air filter relatively clean, but you can always double-check that it’s not clogged and can allow easy air exchange.

If the fans, condenser and air filter are all in good condition, the next troubleshooting step is to measure the system pressures with a manifold gauge set.

Start at the Compressor

Since the compressor is the beating heart of your air conditioning, it only makes sense to start looking for problems at that point, then move through the rest of the system.

To check that your compressor is engaging and functioning, start your truck and set the air conditioning to the max with all of the fans on high. Then look at the front of the compressor where the pulley is located, and ensure that the clutch is engaging properly. The pulley will spin freely until the compressor relay kicks in, which engages the clutch and allows the belt to operate the compressor.

If the clutch seems to be engaging and disengaging after only running for a few seconds, it is a good sign that the system is low on refrigerant. This is because the compressor will start running and fill the system with refrigerant, which causes the local level to drop to a point where it hits a cutoff for low refrigerant. This cutoff prevents the compressor from running without enough refrigerant in the lines, which also acts as a lubricant for the compressor.

If the clutch does not seem to be engaging at all, make sure the compressor is getting power from the system by using a voltmeter or multimeter to check the voltage coming in. If you can’t measure any voltage, it may be a blown fuse, relay or cycling switch. If there is voltage, the clutch may have gone bad, which means the compressor needs to be replaced.

Check for Leaks in the System

A large portion of problems with A/C systems are caused by the lack of proper refrigerant levels. If you have experienced issues related to low refrigerant more than once, chances are good that you have a leak in your system somewhere. Get an air conditioning UV leak detection kit and let the dye circulate in the system. Then let the system rest and inspect for leaks.

Be sure to check around fittings, hoses, manifolds and joinery between hoses and fittings. If there are any leaks, have a professional repair those components, and repressurize the system with more refrigerant and potentially more dye.


Our A/C Experts Are Here to Help!

If you have been experiencing problems with the air conditioning system in your truck, or if it just isn’t blowing as cold as it used to, it may be time to have Blaine Brothers take a look at it. Our team of expert technicians will be able to quickly diagnose problems with your A/C system and repair those issues quickly to get you back on the road. Reach out today for more information!

Blaine, MN


10011 Xylite Street NE
Minneapolis, MN 55449

Cloquet, MN


1325 Hwy 45
Cloquet, MN 55720

Clearwater, MN


750 Heaton BLVD
Clearwater, MN 55320

Baldwin, WI


2500 Alreich Ave
Baldwin, WI 54002



9515 150th Avenue NE
Columbus, MN 55025