6.7 Cummins Heater Blowing Cold Air: Quick Fixes for a Toasty Ride

A common issue faced by many 6.7 Cummins engine owners is the heating system blowing cold air, especially during the winter months. This can be uncomfortable and frustrating, but don’t worry; you’re not alone.

There are several reasons why your heater may be blowing cold air, and this article will walk you through the possible causes and the steps to address this problem.

Understanding the heating system in your vehicle will give you a better idea of what could be causing the cold air issue.

The heating system utilizes the engine’s coolant to transfer heat from the engine to the cab. Issues with the coolant, air blend door, or heater core can all contribute to experiencing cold air when you’re expecting warmth.

Additionally, it’s essential to recognize that any system malfunction can lead to an improperly functioning heater. The key is to diagnose the problem and either handle the repairs yourself or seek professional assistance, depending on the complexity of the issue.

Key Takeaways

  • Identify potential causes for the heater blowing cold air
  • Diagnose and troubleshoot the issue to pinpoint the problem
  • Consider professional assistance for complex repairs and preventative maintenance
6.7 Cummins Heater Blowing Cold Air

6.7 Cummins Heater Blowing Cold Air: Understanding the Problem

Common Signs and Symptoms

When your 6.7 Cummins heater is blowing cold air, you may notice:

  • Lack of warmth coming from the vents while driving
  • The temperature gauge fluctuating or not reaching the normal operating temperature

Why does a 6.7 Cummins Heater Blow Cold Air

There are several reasons why a 6.7 Cummins heater may blow cold air:

  1. Clogged heater core: A clogged heater core can impede the flow of hot coolant, leading to cold air being blown from the vents.

  2. Low coolant levels: If your coolant levels are low, there may not be enough heat being transferred to warm up the air inside the cabin.

  3. Failing thermostat: A malfunctioning thermostat might not be able to regulate the engine temperature properly, causing the heater to produce cold air.

  4. Damaged blower motor: If your blower motor is damaged, it might not be able to produce enough airflow to deliver the warm air properly.

To diagnose and fix the issue with your 6.7 Cummins heater blowing cold air, you should check for any of these common problems and take appropriate action, such as clearing clogs, topping up coolant levels, replacing the thermostat, or repairing the blower motor.

6.7 Cummins Heater Blowing Cold Air

Components of the Heating System

Heater Core and Blend Door

The heater core is responsible for producing warm air inside your cabin. Hot coolant flows through it, transferring heat to the air blown over it by the fan.

The blend door acts as a gate, controlling the amount of hot air mixed with cold air entering your cabin. If the heater core is clogged or the blend door is stuck, it may result in cold air blowing.

Some common issues with the heater core and blend door:

  • Clogged heater core
  • Malfunctioning blend door actuator
  • Stuck or broken blend door

Thermostat and Water Pump

Your thermostat regulates the flow of coolant between the engine and radiator. If it’s stuck open or isn’t functioning properly, it can lead to insufficient engine heating and cold air coming from your heater.

The water pump circulates the coolant. If faulty, it can result in poor coolant circulation and less heat produced by the engine.

Common causes of thermostat and water pump issues:

  • Stuck or failing thermostat
  • Damaged or non-functioning water pump
6.7 Cummins Heater Blowing Cold Air

Radiator and Cooling System

The radiator ensures proper cooling of the engine by dissipating heat from the coolant. A faulty radiator cap might allow air to enter the cooling system, causing air pockets which can lead to uneven heating.

The cooling system’s components, including the heater hoses and coolant, also play a crucial role in maintaining proper engine temperature.

Typical sources of radiator and cooling system problems:

  • Air trapped in the cooling system
  • Damaged heater hoses
  • Faulty radiator cap

The Role of AC in Heating

When it comes to your 6.7 Cummins heater blowing cold air, the air conditioning system plays a crucial role.

The AC is responsible for producing both cold and hot air in your vehicle. If you find your heater only blowing cold air, then there might be an issue with your AC system.

The air flow of the AC system is vital for maintaining the desired temperature within your vehicle. By regulating air flow, the system ensures that the cabin temperature remains comfortable.

If there’s a malfunction with the air flow, it may result in cold air being blown when heat is supposed to be produced.

One common reason for this problem is an air lock, which can occur in the heater core or in the coolant system.

An air lock can prevent proper circulation of coolant, leading to reduced heater performance.

To fix this issue, you can try to bleed the coolant system to remove any trapped air. If that doesn’t help, you may need to check for any blockages within the heater core or AC system components.

To summarize:

  • AC system regulates air flow for both cold and hot air
  • Proper air flow is essential for maintaining cabin temperature
  • Air locks can hinder coolant circulation and reduce heater performance

To address your 6.7 Cummins heater blowing cold air, it’s essential to investigate your vehicle’s AC system for any issues.

By understanding the role of AC in heating and checking for possible air flow or air lock issues, you can ensure that your vehicle’s heating system functions properly.

6.7 Cummins Heater Blowing Cold Air

Troubleshooting and Diagnosis

Checking the Dash Vents and Hoses

Begin by inspecting the dash vents and hoses. Look for any visible damage or clogs that might limit airflow. To do this, you can:

  • Remove the vents and check for obstructions
  • Disconnect and examine hoses for cracks or loose connections

Inspection of Coolant and Thermostat

The coolant level and thermostat condition are important factors in diagnosing the issue. For example:

  • Check the coolant level in the reservoir and refill if needed
  • Monitor the engine temperature gauge and ensure it reaches the normal operating range
  • If the engine is not reaching normal operating temperatures, consider replacing the thermostat
Coolant LevelThermostat Condition
NormalOperating Properly
LowRequires Replacement

Testing the Heater Core and Blend Door

Finally, test the heater core and blend door. These components control the flow of hot coolant and adjust the mix of hot and cold air. To do this, follow these steps:

  • Inspect the heater core for blockages, and flush it if necessary
  • Test the function of the blend door by adjusting the temperature control, and listening for changes in airflow
  • If the blend door does not respond or appears to be stuck, it may be necessary to replace it

By following these steps, you can identify the causes of your 6.7 Cummins heater blowing cold air and take appropriate action to resolve the issue.

6.7 Cummins Heater Blowing Cold Air

Replacing the Blend Door

Replacing a blend door in a vehicle’s heating and air conditioning system can be a challenging task, as it often requires disassembling part of the dashboard.

The process can vary significantly depending on the make and model of the vehicle.

Here’s a general guide on how to replace a blend door, but please refer to your vehicle’s service manual for specific instructions:

  1. Prepare Your Tools and Materials: You will need basic hand tools like screwdrivers, a socket set, and possibly a trim removal tool. Make sure you have the replacement blend door ready.
  2. Disconnect the Battery: Always start by disconnecting the negative terminal of the battery to avoid any electrical issues or accidents.
  3. Remove Dashboard Components: This is usually the most time-consuming part. You may need to remove various components such as the glove box, center console, trim panels, and possibly part of the dashboard itself to access the blend door. Take pictures or notes as you disassemble to ensure you can reassemble everything correctly.
  4. Locate the Blend Door Actuator: The blend door actuator is a small motor that controls the blend door. It’s usually mounted near the HVAC box under the dashboard.
  5. Remove the Blend Door Actuator: Once located, remove the screws or bolts holding the actuator in place. Carefully disconnect any electrical connectors.
  6. Access and Remove the Blend Door: After removing the actuator, you should be able to see and access the blend door. Depending on the design, you might need to maneuver around other components or remove additional parts to get the blend door out.
  7. Install the New Blend Door: Position the new blend door exactly as the old one was situated. Ensure it moves freely and aligns correctly with the actuator.
  8. Reinstall the Blend Door Actuator: Put the actuator back in place, ensuring it aligns correctly with the blend door. Reconnect any electrical connectors and secure the actuator with its screws or bolts.
  9. Reassemble the Dashboard: Carefully reassemble all the parts of the dashboard, center console, and any other components you removed. Refer to your notes or pictures to make sure everything goes back in the right place.
  10. Reconnect the Battery and Test: Once everything is reassembled, reconnect the battery. Test the blend door operation by starting the vehicle and adjusting the temperature controls. Listen for any unusual noises and ensure the air temperature changes as expected.
  11. Check for Errors: If your vehicle has an onboard diagnostic system, check for any error codes that may have been triggered during the process.

Professional Assistance

Dodge Mechanic

A Dodge mechanic is an expert specializing in the maintenance and repair of Dodge vehicles, including those with a 6.7L Cummins engine.

When facing a heater blowing cold air issue, seeking assistance from a Dodge mechanic can be beneficial because they have specific knowledge of Dodge systems and components.

For instance, a Dodge mechanic can:

  • Quickly diagnose the root cause of the problem.
  • Provide the appropriate repair or replacement options.
6.7 Cummins Heater Blowing Cold Air

ASE Certified Technician

An ASE Certified Technician is a professional who has earned certification from the National Institute for Automotive Service Excellence (ASE).

This certification demonstrates that the technician has the knowledge and skills necessary to perform maintenance and repairs on various vehicle makes and models, including your 6.7L Cummins.

Advantages of working with an ASE Certified Technician include:

  • Assurance of high-quality service.
  • Broad expertise in different vehicle systems.
Dodge MechanicASE Certified Technician
Specializes in Dodge vehiclesWorks on various vehicle makes and models
Expert knowledge of Dodge systemsASE Certification ensures broad expertise
Familiar with 6.7L Cummins specific issuesGeneral knowledge of diesel engines, including Cummins

In summary, when dealing with a 6.7L Cummins heater blowing cold air, you can choose to consult a Dodge mechanic for their specialized expertise or an ASE Certified Technician for their broader knowledge and experience.

Whichever option you choose, ensure that the professional is qualified and capable of addressing your issue effectively.

Maintenance and Prevention

Routine Check-up

To avoid your 6.7 Cummins heater blowing cold air, it is essential to perform routine check-ups on your Ram 3500.

Regular maintenance helps identify issues before they worsen. For example, monitor the coolant levels and inspect the thermostat to ensure it’s functioning properly.

Replacing Air Filters

Replacing both the air filter and cabin air filter is crucial for optimal air circulation.

A dirty air filter can negatively impact the airflow through your vehicle’s heating system.

Remember to change these filters according to the manufacturer’s recommendations to keep the heater working efficiently.

Ensuring Proper Engine Warming

Allow your engine to warm up adequately before driving it, especially during colder months.

This process ensures the EGR cooler and other heating components reach optimal operation temperatures, providing warm air on the driver side and floor areas.

Factors to ConsiderImportance in Heater Function
Routine Check-upMaintains overall heating system performance
Replacing Air FiltersEnsures optimal airflow and heating efficiency
Ensuring Proper Engine WarmingAllows heating components to reach operational temperatures

By following these maintenance and prevention tips, you can effectively avoid 6.7 Cummins heater issues and enjoy a comfortable driving experience.

6.7 Cummins Heater Blowing Cold Air

Frequently Asked Questions

Why is my Dodge Ram heater not blowing hot air?

There are several reasons why your Dodge Ram heater may not be blowing hot air, some common causes include:

  • A clogged heater core: Reduced flow of hot coolant can cause cold air to blow from vents
  • Low coolant levels: Insufficient coolant can affect the heater’s performance
  • Failing thermostat: A thermostat that isn’t operating properly can lead to insufficient heating
  • Damaged blower motor: A malfunctioning blower motor can affect hot air circulation

How do I perform a heater core flush on a 6.7 Cummins?

To perform a heater core flush on a 6.7 Cummins:

  1. Locate the heater core hoses, typically near the firewall on the engine
  2. Disconnect the hoses from the heater core
  3. Use a garden hose or similar water source to flush coolant and debris from the heater core
  4. Reconnect the hoses and top off the coolant level as needed

Always consult your vehicle’s manual for specifics on your model.

What is the heater hose diagram for a 6.7 Cummins?

Exact routing and configuration of heater hoses on a 6.7 Cummins can differ depending on the make and model. Consult your vehicle’s manual or an internet forum specific to your vehicle for diagrams and pictures of the correct heater hose routing.

How can I fix my Ram 2500 heater not blowing hot?

Follow these steps to troubleshoot your Ram 2500 heater issue:

  1. Check for proper engine temperature: Ensure the engine is reaching its operating temperature
  2. Check coolant level: Ensure there’s enough coolant in the system
  3. Check thermostat: If the thermostat is stuck open, it may need replacement
  4. Inspect the heater core: Flush the heater core to remove clogs; replace if necessary
  5. Check the blower motor: Ensure it is functioning correctly and providing proper airflow

What are the steps to replace the heater hose on a 6.7 Cummins?

To replace a heater hose on a 6.7 Cummins:

  1. Drain the coolant from the system
  2. Locate and disconnect the old heater hose from both ends
  3. Install the new heater hose and secure the connections
  4. Refill the coolant system and check for leaks

Always refer to your vehicle’s manual for specifics on your make and model.

How can I troubleshoot the heater core elbow on a 6.7 Cummins?

If you suspect an issue with the heater core elbow on a 6.7 Cummins, follow these steps:

  1. Inspect the elbow for visible leaks, cracks, or damage
  2. Check for proper coolant flow through the elbow; if flow is restricted, debris may need to be removed or the elbow replaced
  3. Check the connections and clamps securing the elbow for proper fit; tighten or replace as necessary


In conclusion, addressing the issue of a 6.7 Cummins heater blowing cold air requires a systematic approach to diagnose and fix potential problems.

Regular maintenance, such as checking coolant levels, inspecting the thermostat, and ensuring proper airflow, is crucial. For complex issues, professional assistance from a Dodge mechanic or an ASE Certified Technician is advisable.

By understanding the heating system’s components and their functions, and taking proactive steps for maintenance and prevention, you can ensure a warm and comfortable driving experience in your 6.7 Cummins, even during the coldest months.

Remember, addressing these issues promptly not only enhances comfort but also prevents potential legal and health concerns associated with driving in a cold environment.

Photo of author

Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.