DragRacer383

iTrader: (2)

I'm Robbing stuff from a A/C forum that might help some of you.
If you want the Forum http://www.autoacforum.com/categories.cfm?catid=2


ACCUMULATOR
Accumulators are used on systems that accommodate an orifice tube to meter refrigerants into the evaporator. It is connected directly to the evaporator outlet and stores excess liquid refrigerant. Introduction of liquid refrigerant into a compressor can do serious damage. Compressors are designed to compress gas not liquid. The chief role of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Accumulators, like receiver-driers, also remove debris and moisture from a system. It is a good idea to replace the accumulator each time the system is opened up for major repair and anytime moisture and/or debris is of concern. Moisture is enemy number one for your A/C system. Moisture in a system mixes with refrigerant and forms a corrosive acid. When in doubt, it may be to your advantage to change the Accumulator or receiver in your system. While this may be a temporary discomfort for your wallet, it is of long-term benefit to your air conditioning system.

BLOWER FAN
An electric driven motor/fan used to force air through the evaporator core and/or heater core which’s circulates air through the passenger compartment.

CLUTCH CYCLING SWITCH
Switch used to control evaporator core temperature either by system pressure or an electrical sensing bulb. Clutch cycling switch controls electrical current to the compressor clutch preventing the evaporator core from freezing during operation.

COMPRESSOR
Commonly referred to as the heart of the system, the compressor is a belt driven pump that is fastened to the engine. It is responsible for compressing and transferring refrigerant gas.

The A/C system is split into two sides, a high pressure side and a low pressure side; defined as discharge and suction. Since the compressor is basically a pump, it must have an intake side and a discharge side. The intake, or suction side, draws in refrigerant gas from the outlet of the evaporator. In some cases it does this via the accumulator.

Once the refrigerant is drawn into the suction side, it is compressed and sent to the condenser, where it can then transfer the heat that is absorbed from the inside of the vehicle.

COMPRESSOR CLUTCH
An electro-magnetic coupling that connects or disconnects the belt driven compressor pulley to the compressor shaft.

CONDENSER
This is the area in which heat dissipation occurs. The condenser, in many cases, will have much the same appearance as the radiator in you car as the two have very similar functions. The condenser is designed to radiate heat. Its location is usually in front of the radiator, but in some cases, due to aerodynamic improvements to the body of a vehicle, its location may differ. Condensers must have good airflow anytime the system is in operation. On rear wheel drive vehicles; this is usually accomplished by taking advantage of your existing engine's cooling fan. On front wheel drive vehicles; condenser airflow is supplemented with an electric cooling fan(s).

As hot compressed gasses are introduced into the top of the condenser, they are cooled off. As the gas cools, it condenses and exits the bottom of the condenser as a high-pressure liquid.

CYCLING CLUTCH ORIFICE TUBE (CCOT)
Designation for a system used by GM, Ford, Chrysler and some Imports. Utilizing an accumulator and orifice tube instead of a receiver-drier and expansion valve. The system operates by using a thermostatic switch or a pressure-sensing switch to cycle compressor operation.


DESICCANT
A drying agent used in refrigeration systems to remove excess moisture (molecular sieve or similar substance).

EVAPORATOR
Located inside the vehicle, the evaporator serves as the heat absorption component. The evaporator provides several functions. Its primary duty is to remove heat from the inside of your vehicle. A secondary benefit is dehumidification. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on its surface. Dust and pollen passing through sticks to its wet surfaces and drains off to the outside. On humid days you may have seen this as water dripping from the bottom of your vehicle. Rest assured this is perfectly normal.

The ideal temperature of the evaporator is 32° Fahrenheit or 0° Celsius. Refrigerant enters the bottom of the evaporator as a low-pressure liquid. The warm air passing through the evaporator fins causes the refrigerant to boil (refrigerants have very low boiling points). As the refrigerant begins to boil, it can absorb large amounts of heat. This heat is then carried off with the refrigerant to the outside of the vehicle. Several other components work in conjunction with the evaporator. As mentioned above, the ideal temperature for an evaporator coil is 32° F. Temperature and pressure regulating devices must be used to control its temperature. While there are many variations of devices used, their main functions are the same; keeping pressure in the evaporator low and keeping the evaporator from freezing; A frozen evaporator coil will not absorb as much heat.

HIGH PRESSURE CUT OFF SWITCH
Found mainly on FWD vehicles, this switch will disengage the compressor clutch when excessive discharge pressure is sensed.

LOW PRESSURE CUTOUT SWITCH
Located either in the high pressure or low-pressure side of the system, it disengages the compressor clutch when system pressure drops below a predetermined valve.

ORIFICE TUBE
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 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.

RECEIVER-DRIER
The receiver-drier is used on the high side of systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. The receiver-drier usually has a sight glass in the top. This sight glass is often used to charge the system. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. The use of the sight glass to charge the system is not recommended in R-134a systems as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles. This type of mistake can lead to a dangerous overcharged condition. There are variations of receiver-driers and several different desiccant materials are in use. Some of the moisture removing desiccants found within are not compatible with R-134a. The desiccant type is usually identified on a sticker that is affixed to the receiver-drier. Newer receiver-driers use desiccant type XH-7 and are compatible with both R-12 and R-134a refrigerants.

SIGHT GLASS
A window in the liquid line or in top of drier used to observe the liquid refrigerant flow.

SUCTION THROTTLING VALVES (STV & POA VALVES)
Used on some systems to control refrigerant flow to prevent evaporator freeze-up.

THERMAL EXPANSION VALVE
Another common refrigerant regulator is the thermal expansion valve, or TXV. 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.





Evacuate and Charging Procedure.

Attach a/c manifold gauges to the vehicle. Make sure you attach the correct hose to the proper service port. This is very important to prevent personal injury! Attach center (Yellow Hose) to a UL approved a/c vacuum pump. Open both of the dials on you’re a/c manifold gauge set. This will allow the system to be evacuated through both the low and hide side of the system. Turn your approved vacuum pump on starting the evacuation process. 30 minutes usually will be enough time. If vacuum pump has ballast read the owners manual concerning this option.

When system has achieved a state of 29.9 hg’s of vacuum close both dials on the a/c gauge set. You may loose up to 1 hg for every 1000 feet above sea level depending on the capacity and quality of pump. At this point wait 5 to 10 minutes letting the vacuum boil off any moisture trapped in the refrigerant oil. This is also a good time to watch and see if vacuum has returned to a zero state. If so you need to check for leaks in the system. Assuming the system is holding a vacuum after letting the moisture boil off repeat the evacuation procedure again. This process may need to be done a few times before all moisture has been removed and you see no degradation in vacuum after closing both dials for 5 to 10 minutes.

With both dials closed remove the center charging hose attached to the vacuum pump and connect it to either a can tap and refrigerant or 30lbs refrigerant cylinder. Open the valve on either the can tap or 30lbs cylinder allowing refrigerant into the charging hose. With refrigerant in the charging hose slowly crack this hose at the manifold gauge bleeding off any air that may have gotten trapped when moving from the vacuum pump to the refrigerant source. Only the slightest amount of refrigerant should be released in this process so be sure to tighten the charging line quickly!

Open only the low side dial on you’re a/c gauges allowing refrigerant to flow into the system. Again I stress the high side must be closed or you may cause personal injury to yourself or others! Start vehicle and turn on the a/c system with blower on the highest speed. In some cases if the compressor clutch has not engaged you may need to by pass the low pressure cut out/cycling switch. Refrigerant should be charged as a gas but in some cases it may be necessary to charge as a liquid. Be careful not to slug the compressor with liquid refrigerant! Charge system to OEM amounts and pressures if you are using the refrigerant the system was designed for. If vehicle is has been or is being converted start with about 60 percent of the original charging amount. After getting 60 percent of the original charge slowly add an ounce at a time until you reach the best possible vent temperature and pressure readings. If you do not know what your systems operating pressures are you can use the 2.2 x the ambient temperature as a guide. This should only be used as a guide as many systems will need more or less refrigerant to achieve proper cooling.

Having a weak fan clutch or an inoperative electric fan will cause system pressures to be incorrect. So make sure these components are working correctly before charging a system!

In lower ambient climates, doors and or windows of the vehicle maybe required to be open to achieve proper cooling when charging the a/c system.


Testing a Clutch Coil
Get a 6 foot section of wire with a removable fuse holder. Place a 6 amp fuse in this holder and attach each end to you clutch coil terminals. Fire up the a/c system and if in 10 to 15 minutes its still working you are okay. If the fuse is blown good chance you have a bad clutch coil.


Minimum requirements for converting a system to R134a.

If system has any refrigerant R12 left in the system it must be reclaimed by an approved recovery machine.

Accumulator/drier must be replaced with an R134a compatible replacement. Conversion fittings and label must be added to the system. Label should have the amount of R134a used and quantity and oil type listed. If vehicle is not equipped with a high pressure cut off switch it must be added.

That is the required minimum! Flushing the system to remove the mineral oil and debris should also be done. R134a and mineral oil do not work well together so leaving it in the system with R134a is not recommended! O-rings should be replaced with either NBR or HNBR replacements. Adjustment of the pressure cycling switch may also be needed to achieve the best performance. In some cases an upgrade of the condenser may be required to achieve the original performance.

There are many different suggestions when charging a R12 system with R134a. System must be evacuated before starting the charging procedure. I suggest you start with about 70 percent of the original R12 charge and add an ounce at a time until vent and pressure readings reach the best available results. Remember it is easy to over charge a system with R134a so patience is important.

DragRacer383

iTrader: (2)

More Tips
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.


While performing any service work on a vehicle always inspect the condenser's surface area. Dirt, bugs and any other debris will restrict air flow therefore reducing the condenser's ability to dissipate heat properly. It is recommended that on long haul trucks, off road equipment (construction, logging, mining etc) and agriculture machines that this be done on a regular monthly basis. Also be careful not to bend or damage the fins in the process of cleaning.

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.


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 foreign material.

Did you know?
The most common reason a replacement compressor fails (new or remanufactured) is caused from contaminates from a previously failed compressor

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.

Dangers you should be aware of...
Although it has an ASHRAE designation it has not been accepted by any of the mayor vehicle manufacturers outside of China. Any use of this product will invalidate warranties on OEM products and with Omega. Do not use flames or torches to search for leaks especially with this product.

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.


Heat is present everywhere. A/C systems are designed to remove heat from one place to another. There are three laws that must be present for refrigeration systems to exchange heat from inside a passenger compartment to the outside atmosphere. First of all, Heat travels to cold or less heat. Second of all, Condensation releases or dissipates heat. Last, Evaporation captures heat. Using the laws of refrigeration in a closed loop circuit of components, temperatures can be controlled. I.E. Automotive a/c system.

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.

Summer Checkup, what can you do?
There are different types of checks that can be done on the ac. Most checks include the following. Visual inspection of the compressor and lines for signs of A/C oil leakage, noise inspection, belt inspection, testing the low and high side pressures for the proper amount of refrigerant, A/C output vent temperature test, inspecting and cleaning drain tube, inspection and confirmation of proper fan operation.

Things to do and look for when draining 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?

Did you know?
Some new compressors can leave the factory without an oil charge but checks and balances in most manufacturer's processes at several different stations that check precise weights of individual and pallet compressors and electronic monitors at the filling station make it hard to pass through. To be on the safe side always check your new compressor for oil.


3rd Gen Tip or any Gm useing a Orifice tube.

Replaceing your GM O tube with a Ford blue tube will give better cooling peformance with 134a

GM White .072 Orifice, Single black o-ring

Ford Blue or Black .067 Orifice, 2 Green o-rings

The Ford O tube is a dirct replacement. If you need help finding one, Ask for one for a 89 Bronco they should list Blue and Red. You want the Blue.

Beachmonkey6

Thank you!