What is an Orifice Tube?

Like most of the systems in your truck or fleet, the heating and cooling system is comprised of a complicated network of parts and components that all work together for the same goal — to make sure the temperature in your cabin stays exactly as hot or cold as you want it. The success of this system depends on the performance of every single part from the blower motor to the O-rings.

Because this system is so intricate, it can be easy to not understand everything about how it works. As long as that fresh, cold blast of AC comes on when you turn the truck on, that’s usually all that matters. But it’s also important to gain a better understanding of the small heroes inside your heating and cooling system, such as the orifice tube.

How an Orifice Tube Works

To understand and appreciate the hard work of the orifice tube, we have to start with the AC evaporator. The evaporator is one of the main parts of your truck’s cooling system, and it is responsible for removing heat from the air and also for harnessing refrigerant in its liquid state. This is where the orifice tube comes in.

So, how does your evaporator know how much refrigerant it needs? You guessed it — the orifice tube. The orifice tube controls the amount of refrigerant entering the evaporator, and its diameter matches those of the evaporator system for smooth engagement without leaks. As the orifice tube contains no moving parts, vehicles that use these parts also need to employ an additional method of controlling refrigerant flow. Two of the most popular methods of doing this are cycling the compressor, or turning it on and off at appropriate times, or installing an additional valve inside the compressor that can adjust the pumping capacity. The orifice tube also serves as a dividing line between the high and low pressure sections.

Is an Orifice Tube the Same As An Expansion Valve?

If you’re wondering if orifice tubes have any relation to expansion valves in an air conditioning system, then you’re correct. Orifice tubes and expansion valves perform the same operation — to serve as an inlet to the evaporator. But while these two parts are very closely related, they are not the same thing.

As mentioned earlier, orifice tubes have no moving parts and, more often than not, require an additional means of regulating refrigerant flow. The expansion valve does contain moving parts, including a self-contained meter system to regulate the refrigerant flow from the compressor to the evaporator. Most modern vehicles use either an orifice tube or an expansion valve depending on your make and model.

Do Orifice Tube Colors Mean Anything?

If you’ve ever seen an orifice tube, then you know that they’re all different colors, from maroon to dark gray or purple. While you may have a personal preference of a blue orifice tube going on your truck rather than a yellow or brown one, the colors do matter.

Orifice tube colors correspond to the orifice diameters of different makes and models of trucks. So when you need to replace this part, not just any color will do. If you have an orange orifice tube, in other words, you are not able to replace it with any color that’s available. It always has to be orange to correspond with the truck’s orifice diameter.

When To Replace an Orifice Tube

One of the benefits of having an orifice tube instead of an expansion valve is the minimal maintenance that these parts require. Since an expansion valve has moving parts, it can experience loss of proper metering or sticking open or closed after time. An orifice tube does not have these issues, but it can become clogged with debris over time, at which time a replacement is necessary.

Shop our online catalog or call today for top quality orifice tubes from Red Dot, a trusted brand with over 65 years of HVAC experience. With strategic distribution centers across the country, we can get you your Red Dot orifice tube where you need it and when you need it.

Key Points: Orifice Tubes Are Your AC’s Unsung Heroes

  • Your AC system has a lot of moving parts, including the orifice tube
  • The orifice tube divides the high and low pressure sides of the HVAC system and regulates the flow of refrigerant into the evaporator
  • The orifice tube is very similar to an expansion valve, but the orifice tube has no moving parts and is not as susceptible to malfunctioning
  • Orifice tubes should be replaced when they are clogged with debris

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