DodgeForum.com

Dodge Ram 2002-2008: Air Conditioning (A/C) Diagnostic

Do you want to understand what may cause your Ram's A/C system to fail? In this article you will read some of the common problems that occur inside the A/C system and how you can fix them.

By Neftali Medina - July 20, 2015
Contributors: Traceline, DoitYourself, DodgeTalk

This article applies to the 2nd Generation Dodge Ram (2002-2008).

You're driving down the highway enjoying the fact that you have ice cold A/C keeping the weather inside the cabin feeling nice, as oppose to the scorching heat being experienced just outside your windshield. Suddenly the cold air stops, and instead begins expelling that same feared heat into the cabin. There are several issues that can cause this to happen due to the complexity of the inner workings of an A/C system. Each part requires the system to be properly sealed; otherwise, the components, such as a compressor or condenser, are subject to fail. These following instructions will help describe some common problems that can cause the A/C system to fail.

Materials Needed

  • Cooling system UV dye
  • Black light
  • A/C refill can
  • Test light

Step 1 – Check the fuses

The fuse(s) may have blown.

Although this is rarely the root cause of an air conditioning problem, a blown fuse or damaged relay could be the reason why the A/C stopped blowing cold.

  • Pop the hood of your truck, and grab your test light.
  • Locate the A/C fuses and begin checking each unit.
  • If the fuses do not show any connectivity, then proceed to replace them.
Figure 1. Dodge Ram under-hood fuse box.

Pro Tip

Although replacing a damaged fuse will correct the current issues, you should be aware that something caused the fuse to blow and there may be a larger problem in the system's wiring. If the fuse blows again soon after being replaced, check the wires that routes to it.

Step 2 – Check for leaks

The refrigerant may be escaping.

The A/C system is pressurized, meaning that it operates under instances of high to low pressure. The refrigerant is forced through the system by the compressor, then through the condenser, drier, expansion valve, and the evaporator. The system uses approximately 200 psi of pressure to push the air through the lines and drops down to roughly 35 psi after making a full cycle. Your Dodge Ram takes approximately 1 lb. (16 oz) of refrigerant. If there are any holes in the system, the refrigerant will begin to leak, causing the air to become less cool.

  • Inject a special cooling system UV dye into the low pressure port of the system.
  • Allow the compressor to run, and blast the A/C for several minutes.
  • Turn the truck off and allow the engine to cool off.
  • Shine a black light onto the cooling system components.
  • Inspect the joints or anywhere there are fittings involved.
  • Replace the leaking components.

Related Video: How to Find an AC Leak with UV Dye

Pro Tip

If there is no refrigerant left in the system, you will need to buy enough to fill it. Also be ready to inspect any of the components, as the leak could have caused contaminants to enter the system and cause damage.

Step 3 – Check the condenser fan

The condenser fan motor may have died.

The condenser fan is designed to keep the heat away from the A/C system. When the fan stops working, Freon will heat up and be unable to cool down quickly, causing the vents to blow hot air at times. To check the condenser fan, open the hood and observe if the fan turns off when the engine is running. If the fan does turn off, you will need to replace it.

  • Remove the two bolts from the fan housing.
  • Pull the condenser up and remove the four fan screws.
  • Remove the fan from the condenser.
  • Unplug the fan motor.
  • Install the new condenser fan unit.
Figure 3. Check the condenser fan.

Pro Tip

Before removing the fan, make sure the condenser relays and fuses are in working order as they would cause the same types of symptoms if damaged.

Step 4 – Check the A/C compressor

There might be no pressure.

The A/C system compressor is considered the heart of the cooling system, as its purpose is to pressurize the refrigerant that cycles through the system. It pushes it out 200 psi of pressure, and then re-absorbs the pressure at approximately 35 psi. When the compressor fails, the air will no longer be able to cool and it will stay hot. There are several issues that can cause this, such as a contamination, overheating issues, lack of lubrication, or an electrical fault. To inspect the system:

  • Start the engine and blast the A/C.
  • Pay attention to the clutch and see if it engages.
  • If it's not engaging, replace the A/C compressor unit.
Figure 4. New Dodge Ram A/C compressor unit.

Pro Tip

Although most replacement compressors come with oil already inside, you may have to add some yourself. Your Dodge Ram compressor is rated for ND8-PAG oil.

Related Discussions and Video