Automotive Air Conditioning (AC) Maintenance Tips

If you would like a friendly weekly reminder of some effective (A/C) maintenance tips.

Signup for weekly email tips

Did you know that...the refrigerant oil color can often provide us with some idea of the compressor and internal system conditions? Black Oil indicates carbonization caused by air (moisture) in the system. Brown Oil indicates copper plating caused by moisture in the system. Grey or Metallic oil indicates bearing wear or piston scoring. Piston scoring may be attributed to high head pressure caused by system moisture.

Did you know that... The most common expansion valve failure mode is due to valve charge head leaks. System contaminants lodged in the valve inlet orifice may also affect valve metering and flow capabilities. Suspected metering inconsistencies many time have distinct characteristics. Starving Expansion Valve: Frost will form on the inlet of evaporator Flooding Expansion Valve: Hissing at valve upon system shutdown

COMPRESSOR DRIVE BELT MAINTENANCE... There are several factors that have major effects on compressor drive belt life expectancy and reliability. Belt alignment and proper tension are the two most critical and controllable by the installer and end user. When improperly installed or maintained drive belts can cause significant damage to the compressor and clutch and other components as well as pose a safety issue.

Did you know that the process that causes fittings to seize up is called electrolysis. To help prevent this apply mineral oil to the threads of the fittings then tighten to the proper torque. Also apply to the o-rings to help them seat properly.

Did you know that Most clutches fail due to low voltage which causes them to slip and create extreme heat. If the clutch face is discolored that is possibly the case. You may also see some epoxy from the coil windings that may be there as well. To see if this is the problem, start the vehicle and turn all of the accessories on. With a volt meter check the voltage to the clutch and make sure it's to the manufacture's specifications. If the voltage is all right then there is a problem with high head pressure.

Using the correct orifice tube......... Color is not just to look pretty, they actually identify vehicle families and different orifice diameters......... some people substitute white for yellow in Volvo and red for blue in Ford, that may work but does not necessarily provide maximum efficiency. Always follow the manufacturers recommendations for the exact color and fit. All of Omega’s orifice tubes meet or exceed manufacturers specifications.

Did you know that... ...The most common expansion valve failure mode is due to valve charge head leaks. System contaminants lodged in the valve inlet orifice may also affect valve metering and flow capabilities. Suspected metering inconsistencies many time have distinct characteristics. Starving Expansion Valve: Frost will form on the inlet of evaporator, Flooding Expansion Valve: Hissing at valve upon system shutdown.

Did you know that... ...The primary function of a receiver drier is to remove moisture from the system. Under normal operating conditions the drier canister should be warm to the touch. The presence of frost on the canister indicates an internal restriction.

Did you know...When replacing a heater core be sure to purge the air from the system when refilling the coolant. Air in the system is a common characteristic of poor or no heat conditions after core replacement.

Remember to always check your newly purchased compressor for oil. Now many new and rebuilt compressors come without oil. Inadequate or excess oil in the system will cause loss of performance and compressor damage as well as other component damage.

When contaminants build up on the evaporator fins, such as dirt, dust and other debris, it's ability to absorb and remove heat from the cab can be severely reduced as well as restricting the air flow. To maintain peak performance, regularly clean the fin area with a fin comb and solvent and change the cab air filter if applicable. Take special care to not bend or damage the evaporator fins in the process.

The receiver drier filters out contaminants in the a/c system and removes moisture to protect the system from internal corrosion. Never leave the drier uncapped prior to installation and should be the last component replaced during any service of the HVAC system. In a preventative maintenance schedule it is recommended the receiver drier be replaced every 12 months.

Use only Department of Transportation (DOT) approved cylinder for storing used or recycled refrigerant. Approved cylinders are stamped DOT 4BA or DOT 4BW. Store in approved cooler locations (avoid heat) High heat can raise internal pressure to dangerous levels.

Do not use open flame around refrigerants. Avoid combustion engine operation when refrigerant leak is detected near intake area. If accident occurs leave area immediately. WARNING: DO NOT BREATHE ENGINE EXHUAST OF COMUSTED REFRIGERANT FUMES!

Turn off switches and disconnect battery ground cable when working on electrical motors or any controls, also if arc welding on a vehicle.

If pressure readings were diagnosed to require adjustment, then most likely it was determined that some loss of refrigerant has occured. So depending on the amount that needs to be added, how sever is the problem? Was it a very small amount that could be called normal permeation or a larger amount indicative that a repair is required? In either case the correct thing to do is to carefully go over the system and fix any leak that can be identified. It is only going to get worse. Fix any leak that can be identified.

It is recommended to install liquid line filters and suction screens when previous system failure was the result of compressor, accumulator, or receiver drier failure. Additionally, flushing the system with like refrigerant is recommended as needed.

Clutch slippage is a common cause for clutch and or compressor failure. The heat created when a clutch slips can damage the pulley bearing and weaken the compressor shaft seal. During any service work to the a/c system always check voltage to the clutch coil and air gap between the hub and pulley to prevent slippage.

A binary pressure switch is a compressor safety device that has 2 distinct functions. The first function cuts the compressor off if the refrigerant charge is lost or too low to prevent the compressor from running dry and locking up. The second function cuts the compressor off if the head pressure reaches unsafe levels to prevent compressor damage or damage to other components such as a blown hose. Always install the binary switch on the liquid side of the a/c between the condenser and expansion valve.

The most common block valve failure is loss of gas charge inside the power element head. Plugged expansion valves cannot be flushed out and must be replaced. When replacing a capillary type expansion valve make sure the capillary coil or bulb is properly attached to the outlet side of the evaporator line and well insulated with prestite insulation tape.

The receiver drier stores excess refrigerant, filters out any contaminants that may be in the system and removes moisture from the liquid refrigerant to protect the system from internal corrosion. Placement should be between the condenser and evaporator inlet and should be warm to the touch with the a/c running.

Poor system performance could be faulty reed valves. A hissing sound from the compressor immediately after shutdown indicates high side to low side pressure leakage. To check this, attach manifold gauges and turn compressor on. Readings showing lower than normal discharge pressures and high suction pressures or a rapid stabilization of gauge readings shortly after shutdown indicate leaking reed valves or head gasket.

When replacing the clutch assembly always make sure to re-install the snap rings properly. Snap rings have two sides, one is flat and the other beveled. The beveled side should always go to the outside to ensure proper fit.

Always flush the A/C system to remove any contaminates and replace any parts that cannot be flushed. It is also a good practice to use inline suction filters to help catch any foriegn material.

Always be aware of Refrigerant Replacements. R-415b is being touted as an R12 and in some cases an R134a replacement. This refrigerant ASHRAE Name : R-415b(25% HCFC-22 / 75% HFC-152a)is a BLEND and is also highly flammable. We at Omega do not recommend the use of this blend for any of our customers.

When working with either PAG or Ester oils always be sure to keep the container capped when your not using. The chemical makeup of these types of oils will absorb moisture and can create a problem in the a/c system later.

A/C systems can be contaminated with metal particles from the normal wear of the compressor and tiny amounts of water moisture. Contamination can cause a system to fail. Protection against contamination is provided by the filter screen on the Expansion Tube and the desiccant in the bottom of the dryer or accumulator. Other forms of contamination may be the wrong kind of oil, wrong kind of liquid charge or other material that will interfere with the cooling system. Almost 100% of moisture is normally removed from the system when it is evacuated prior to installing (R12 or R134a), but flushing the entire system will be the only way to remove any particles.

When either installing a new a/c system or doing a service job always make the drier the last component replaced before evacuation and recharge. The desiccant in the drier absorbs moisture and will decrease performance and create a problem to the system at a later date. Moisture and refrigerant when combined creates an acid and will damage the internal parts of the a/c system.

Things to do and look for when drainging oil from a compressor... 1) At what ambient was the comp drained at? Hot = more drained oil, Cold = slow/ less oil. 2) Were the ports / caps removed to prevent a vacuum? 3) Was the oil drained and measured from the cylinder head as well as the compressor body? 4) Please remember that depending on the temp at time of draining that aprox 1/2+ oz will remain in the compressor. 5) When the compressor was drained was the compressor crank turned or rotated? 6) How long was the compressor drained?

The orifice tube often has a mesh screen and is found in the evaporator inlet pipe. 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 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.

What's the musky smell out my vents? The first component to check is the drainage tube. If the tube is blocked it will trap the water and cause mildew to set it. Some vehicles have a foam type material that surrounds the evaporator. If this foam becomes wet from condensation or other means then it also has the tendency to cause the musky smell. There are procedures that can be done to eliminate the problem. Call your Omega representive for information on the products specifically designed for A/C vent odors.

Checking Compressor Oil Color and what the colors mean to you... a. Black - Air in the system causing carbonization b. Brown - Moisture causing copper plating c. Grey or Metal Shavings- bearing and/or piston wear, therefor you must flush the system, replace the Receiver/Drier and evacuate/recharge.

We believe if the a/c system is opened for service, it's a good time to flush. A clean system minimizes the chance of a comeback. On systems that utilize an orifice tube, you can usually judge the condition by looking at the inlet side of the orifice tube screen. If a substantial amount of debris were found, flushing would be recommended. Likewise, visual inspection of the refrigerant oil may indicate it's time to flush. Any time that a major component fails system flushing is required.

Putting a larger displacement compressor on a vehicle rarely makes it perform better and in some cases it can actually decrease performance. Most systems are designed for specific performance goals. These goals are determined by a number of factors: glass area, interior space, projected heat load, engine operating RPM, just to name a few. After all these factors have been calculated, the heat exchangers are designed for a specific BTU range. The compressor is then selected for the application