ORIFICE TUBES
The orifice tube, probably the most commonly used, can be found in most GM and Ford models. It is located in the inlet tube of the evaporator, or in the liquid line, somewhere between the outlet of the condenser and the inlet of the evaporator.
This point can be found in a properly functioning system by locating the area between the outlet of the condenser and the inlet of the evaporator that suddenly makes the change from hot to cold. You should then see small dimples placed in the line that keep the orifice tube from moving.
Most of the orifice tubes in use today measure approximately three inches in length and consist of a small brass tube, surrounded by plastic, and covered with a filter screen at each end. It is not uncommon for these tubes to become clogged with small debris.
While inexpensive, usually between three to five dollars, the labor to replace one involves recovering the refrigerant, opening the system up, replacing the orifice tube, evacuating and then recharging.
With this in mind, it might make sense to install a larger pre filter in front of the orifice tube to minimize the risk of of this problem reoccurring. Some Ford models have a permanently affixed orifice tube in the liquid line. These can be cut out and replaced with a combination filter/orifice assembly. |
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THERMAL EXPANSION VALVE
Expansion Valve, Expansion Tube, TVX. Also called the orifice tube. This component often has a mesh screen and is found in the evaporator inlet pipe (liquid line). In some cases this item is found in the outlet of the condenser. Its purpose is to limit the flow of the high pressure liquid (R12 or R134a) and thereby meter the flow of refrigerant to the evaporator as a lower pressure liquid. The screen serves the purpose of trapping metal particles that break loose from the compressor or other components. Expansion Valve come in two types, Block and Right Angle. The block valve is located at the evaporator and its purpose is to constantly check the temperature of the (R12 or R134a) and allow the proper amount of (R12 or R134a) to enter the evaporator. The right angle valve comes in two types (internal equalized and external equalized). This valve is also found before the evaporator and its purpose is to control the amount of (R12 or R134a) going into the evaporator.
Commonly used on import and aftermarket systems. This type of valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type. This type of valve is usually located at the firewall, between the evaporator inlet and outlet tubes and the liquid and suction lines. These types of valves, although efficient, have some disadvantages over orifice tube systems. Like orifice tubes these valves can become clogged with debris, but also have small moving parts that may stick and malfunction due to corrosion.
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A/C BLOWER MOTOR
The blower motor mounts to a housing surrounding the heater core, evaporator and air control doors.
Purpose: The A/C blower motor moves air from outside the vehicle, through a cabin air filter if equipped, then through the heater core, and/or evaporator based on driver demands. The air control doors control the exact direction of airflow from the blower motor. The resulting airflow then warms or cools the interior, or is used to de-fog or de-ice the windshield.
Maintenance Tips / Suggestions: Symptoms of a A/C blower motor or circuit problem include no airflow when the blower is turned on, a noisy blower motor, or a blower motor that only operates at some speeds. Some blower motor problems may be as simple as a blown fuse (see your owner?s manual) or a bad connection. For best results, have the A/C blower motor circuit checked by a professional technician. |
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