WHY AN EXACT AMOUNT OF FREON
Today's systems use smaller amounts of freon. No longer is it 2 to 4 lbs, but rather 18 to 38 ozs. With tight compressor tolerances and lubricant mixed with the freon, the mixture must be just right to enter the compressor as a mist. Wrong mixtures will either under lubricate or slug the compressor causing premature failures. You don't know how much liquid freon is in a system so you should recover the old freon, evacuate and add the correct charge. Always check the OEM spec for the correct charge.

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DANGER ! CHARGE WITH VAPOR - NOT LIQUID
If a charging hose is long enough you might get away with using liquid refrigerant because the liquid will partially change to a gas in the hose. More often you will freeze and shatter the compressors valves when the refrigerant hits the valves as a liquid.

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CLUTCH FAILURE
Some common causes for clutch failure:

1. Bearing failure: Use of worn re-packed bearings
2. Air Gap: Between the outer plate (hub) and the belt/rotor (.016 -. 030 inch) Note! Air gap varies with compressor type - check OEM specs.
3. Shorted Coil: Correct coil resistance is 3 - 5 ohms.
4. Low voltage at coil will cause coil to overheat due to slippage.
5. Locked Compressor: Excessive discharge pressure - Check for restricted condensers, receiver/driers or an oil over charge
6. Belt is wrong type, wrong size, miss-aligned or loose.
   

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FALSE PRESSURE READINGS

• Before connecting manifold gauges you should check:
• Are the pointers aligned to zero
• Are the valve core depressors and hose gaskets not damaged
• Are the service hoses connected to the correct service valves
• Is the engine running at 12-1500 rpm with a strong external fan blowing into the condenser.
• Is the system correctly charged with the correct refrigerant? Blends will give different readings than pure R12 or R134a.
• R12 systems retrofitted to R134a will read approx 10% higher discharge pressure than the R12 systems.

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CAUSES FOR COMPRESSOR FAILURES
LACK OF USE:
Compressors not run regularly will be starved for lubrication when they are turned on. This causes excessive ware until the oil again reaches the compressor. It's best to use the A/C once a week for a few minutes. FAILURE TO FLUSH SYSTEM:
Compressors and hoses wear causing bits and pieces to mix with the oil. This sludge gets into the compressor and can cause it to seize. Failure to properly flush or using flush that leaves a residue is a primary cause of failure.
EXCESSIVE HIGH OR LOW PRESSURE:
Condenser fans can quit due to bad connections or defective motor windings that get too hot. This creates excessive head pressure and heat that can lock up or damage a compressor. Loose connections at the coil can cause high resistance and low voltage causing clutch slippage. Low refrigerant charge will cause lack of lubrication getting to the compressor. Painting condensers will insulate them from efficiently removing heat and increase head pressure in the compressor.
IMPROPER FREON OR OIL CHARGE:
Compressors manufactured after 1990 have smaller capacity, therefore use less refrigerant and oil and are extremely sensitive to inadequate amounts of oil. The wrong type of oil may break down in high heat conditions. R134a systems are more sensitive to lubrication than R12 systems. An over charge of oil can clog the condenser, the orifice tube or expansion valve and starve the compressor of oil. R12 systems use mineral oil and R134a systems use PAG or Ester lubricants (always check the OEM specs)
REFRIGERANT BLENDS
They can affect seals and O-rings, causing them to leak, swell or otherwise deteriorate and it can happen relatively quick.

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PRINCIPLES OF ELECTRICITY

OHM'S LAW, simply stated - it takes one volt to push one ampere of current through one ohm of resistance
(voltage = amps times resistance)
(amperage = voltage divided by resistance)
(resistance = voltage divided by amperage)

WATTAGE is the amount of electricity applied to do work. One watt equals one volt times one amp or one volt amp (VA)

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WHY REFRIGERANT 134a
R12 has the ozone depleting chemical chlorine in it and has been replaced with a refrigerant known as R134a. A boiling fluid absorbs heat and changes its state to a vapor. The expanding vapor/gas has a lower pressure than the liquid and therefore lower temperature. For heated air to be absorbed it must transfer to a cooler surface. The trick is to find a liquid that boils at such a low temperature that the vapor is cold enough to absorb the amount of heat generated inside an automobile. Freon-12, a DuPont trade name, boils at -22 degs F and its expanding vapor, in the evaporator core, absorbs the heated air circulating around it. Freon-134a boils at about the same temperature as R12 and therefore is a good replacement.

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HUMIDITY AND YOUR AIR CONDITIONER
You're A/C unit works to remove heat from the passenger area and in doing so it also removes moisture. We are most comfortable when the relative humidity is closer to 20 percent than 90 percent, therefore the A/C system expends most of its effort wringing moister out of the air. This is what air conditioning is all about - conditioning the air. It's important to check the condensation drain at the bottom of the evaporator. If you see clear water dripping from your car, when parked… it's a good thing…if it's from the evaporator.

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AIR CONDITIONING ODORS
A/C evaporator odors are a continual complaint. If condensation cannot drain from the evaporator, the water stagnates, bacteria and viruses grow in the water and odors occur. It is always a good idea to keep the outside air inlet screen clean.

1. ORGANIC ODOR: Odor from airborne fungus.
2. CHEMICAL ODOR: Odors emitted by the anti-corrosion coating on the evaporator. Most noticeable when the system is running very cold.
3. DUSTY ROOM ODOR: High performance evaps use thin alloys with high fin count which traps water on the evap face causing the anti-corrosion coat into come off and breed the fungus.
4. New products that are foaming sprays clean out the mold fungus and bacteria from the evap case where they grow.
   
   
   

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O-RINGS - NOT ALL THE SAME
O-rings were once only a matter of size. Now it's a matter of correct material. Both R12 & R134a use Green O-rings made of HNBR material
BUNA-N Black in color and use with R12 ONLY
TECHSEAL Black in color used with Spring Lock fittings due to its resistance to compression. Use with R12 ONLY
HNBR Green in color - use with R12 & R134a equipped A/C's Use of the incorrect type will cause degradation and leakage.

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WHERE DOES THE HIGH SIDE START
Where ever the dam is located is the separation point. I call it a dam because it has high pressure on one side and low pressure on the other. This separator is call an Expansion Valve or an Orifice Tube. Its job is to allow only enough refrigerant through to allow gas expansion in the evaporator. By limiting the flow of gas it creates the high pressure back to the compressor.

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BLACK DEATH!
Black Death, as it is known by A/C techs, is a result from the breakdown of the refrigerant-lubricant. This causes excessive wear inside the compressor and the excessive ware causes a black residue that is actually a combination of solder flux from the condenser and aluminum shavings from the old compressor. When this goop cools, it hardens in the condenser. Repeated flushing will not remove it, however, when the system is charged and running it liquefies, flows out into the liquid line and clogs the orifice tube. With less refrigerant flowing, past the orifice tube, the compressor is starved of lubricant and will lock up. The only answer is to replace the condenser.

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WHAT DOES A DRIER DRY?
It's not the freon!! It's the oil in the refrigerant that absorbs moisture and holds debris in the system. Replacing the drier or accumulator, in addition to evacuation, will assure better performance. Be sure your new drier or accumulator has the new XH7 or XH9 desiccant that is recommended for all refrigerants.

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INSIST ON FLUSHING
Oil, sludge and debris that is left in the system can clog the condenser, orifice tube or expansion valve and damage the compressor. Flushing removes excess oil and debris from previous services. You do not want to add yet another charge of oil while leaving an unknown amounts of oil in the system.

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SYSTEM LEAKS - Find the small ones!
At one time freon was cheap and a 2oz. per year leak was acceptable in a 4-5 lb. System. Today systems are smaller and 1/2oz makes a big difference in performance. Good halogen leak detectors will show most system leaks, under static conditions, however some will leak only when the system is in operation. This is where the insertion of a florescent dye can help find the leak. Note, to see the dye stain you need a UV lamp and the leak has to be where the light can reach it. Most car manufactures approve the use of trace dyes and some OEM's have been inserting trace dyes on the assembly line. Dye can be inserted either when charging or when the system is charged. The amount of dye used is less than 1/3 oz and remains in the system even if the total charge is lost. The dye stains the oil not the freon and only flushing will remove it.

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GLOSSARY OF TERMS
ACCUMULATOR: stores & filters freon (on Low side of system)
BTU: British thermal unit
AMBIENT AIR: outside air
CAPILLARY TUBE: gas filled temperature-sensing tube
CCOT: clutch cycling orifice tube that replaces the
TXV CLUTCH CYCLE SWITCH: evap temp controlled switch that cycles clutch COMPRESSOR: pump that moves the refrigerant.
CONDENSER: heat exchanger-removes heat from refrig
DISCHARGE LINE: compressor outlet line DRIER: filters refrigerant (located on High side of system)
EPA: Environmental Protection Agency
ESD: Electrostatic Discharge
EVAPORATOR: heat exchanger-removes heat from air
HEAT: anything above absolute zero has heat
HEAT EXCHANGER: device for transferring heat
LIQUID LINE: moves high-pressure liquid through system
MANIFOLD: connects suction & discharge lines to compressor
PAG: Polyalkylene glycol (lub used with R134a refrigerant)
PROM: Programmable Read Only Memory - use in computers
SUCTION LINE: between evaporator outlet and compressor
TXV: thermostatic expansion valve - maintains evaporator

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WHAT IS A TON OF REFRIGERATION?
One Ton of refrigeration is defined as amount of heat (288000 Btu's) required to cause a change in state of one ton of ice to one ton of water at 32 degs. F in 24 hours.
A/C units are rated by Btu/hour ratings. A one ton unit is rated as 12000 Btu's (288000/24) The average factory installed auto A/C unit is rated at 1-3/4 ton.

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CONDENSER DESIGNS - OLD and NEW
R134a condensers have more fins/inch than R12 condensers and their fin diameters are smaller.
( 6mm)






TUBE and FIN - Oldest industry standard, 3/8-inch diameter round tube condenser. Ok, for R12 but not recommended for R134a.





6 mm PICCOLO multi-flow: smaller, lightweight and more efficient than 3/8-inch tube and fin and serpentine. Used in many domestic OE applications.







SERPENTINE: All aluminum, more efficient than tube and fin, used on smaller imports where space is limited







PARALLEL FLOW: all aluminum, this efficient design breaks up flow into tiny streams that give up heat more rapidly.






PARALLEL FLOW with SUB Cond. Oval tube multi-flow and sub-condenser stacked up. Refrigerant flows through the multi-flow into the drier (called a modulator) then continues as a liquid into the sub-condenser.

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  DA6/HR6 Compressor "Lock Up"
A problem with DA6/HR6 compressors is the piston rings come off the pistons and get stuck in the condenser. If the condenser has two rows of coils and one is stopped up the other row will be forced to carry the total pressure load. One row of coils handles approx. 225 PSI; therefore, more pressure will cause the gas to back up to the compressor causing it to lock up. Hi side service valves located after the condenser will read LOW discharge pressure when the condenser is not letting all the gas through. Touch the condenser in several places to see if it is equally hot. A cool spot is an obstruction. It's impossible to flush out a piston ring. The only solution is to replace the condenser.

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EXCESSIVE CLUTCH CYCLING
It's common to assume low refrigerant is the cause for excessive clutch cycling and this often leads to adding refrigerant and thereby overcharging the system. Most vehicles have a compressor clutch cutout strategy based on an engine coolant temperature of 220 - 240 degs F. The vehicles computer relies on a coolant temperature sensor to provide the signal for the compressor clutch decision and if the sensor reads too high the clutch will cycle off. Cooling systems with a 50-50 anti-freeze mix and the proper radiator cap should boil at around 275 degs, so the system may not be boiling when the compressor cuts out. Check the actual coolant mix and temperature by using an Infrared thermometer to check coolant temperature and a Scan Tester to tell you what temperature the sensor is actually signaling to the computer.

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WHY WE HAVE AIR PRESSURE
Approximately 600 miles above us is a belt of gas that surrounds the earth. This gas belt could be thought of as an ocean of gas and it pushes down its weight upon the earth till at sea level it weighs 14.69 pounds per square in (psi). This means that for each 1000 feet altitude we loose 1.1 pound of pressure and as we go below sea level (as in Death Valley) the air pressure increases beyond 14.69 psi. This is important when you are reading pressure on your service gauges. It is also why you cannot pull a good vacuum in the mile high city, Denver

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  BE SMART! Don't replace Kehin Compressors
During the 1980's the Kehin compressor, used on Hondas, was their hottest seller. That was because it was not a very robust compressor. If one fails, install a Sanden with an adapter kit. Even Honda markets a Sanden conversion kit and will suggest the changeover

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  WHERE DOES THE MOISTURE GO?
Moisture in an A/C system combines with the lubricant and is not easily removed by simple evacuation. Moisture, left in a system, can cause icing inside the system and form a blockage restricting refrigerant flow. A vacuum pumps effectiveness varies with its age, condition, altitude, and any restrictions in the inlet hoses. Before evacuation, replace the Accumulator/Drier and lubricant as the best solution to a system that has been contaminated or left open to the atmosphere. Remember that not even a good two-stage vacuum pump will read -29.9 psi (best possible) as the altitude, where used, rises. It will read 1.1 psi less for each 1000 feet altitude.
Example: In Denver the best vacuum reading is -24.5 psi.

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ELECTROSTATIC DISCHARGE (ESD)
During the testing and repair of computer controlled vehicles we come in contact with components that may be damaged by ESD or static electricity. When installing new electronic components, the part itself may have developed a charge from contact with the package during handling; therefore you need to ground yourself to the body ground of the vehicle. This is easily done by using a wrist strap that is available at most electronic supply stores (Radio Shack)

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  WHAT'S IN A "BLEND" REFRIGERANT
This is only a guideline of representative percentage values of blends

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  COMPRESSORS NEW - REMAN- REBUILT
NEW compressors are pricey and may cause you to loose a repair job. REBUILDERS tend to reuse worn seals, O-rings and repack clutch bearings. REMANUFACTURED compressors cost a little more because they use new bearings, seals, O-rings and piston rings. USE REMANS

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COMPRESSORS TAKE THE HEAT
A compressor can take the heat, but if there's a condenser airflow problem, overcharge, poor lubrication, restriction, etc., the temperature can greatly rise and cause the compressor to seize. Some vehicles have compressors mounted low in the engine compartment and due to poor airflow the compressor can overheat and fail

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OILS ARE NOT ALIKE - TAKE CARE
The moving parts of a compressor must be lubricated during operation. The oil is absorbed into the refrigerant that carries it through the compressor as a mist. An oil over/under charge can damage the compressor. Compatibility of refrigerant oil is determined by its ability to remain oil when mixed with the refrigerant and not become separated by a chemical reaction. R12 systems use a non-foaming sulfur-free grade of mineral oil (YN-9) formulated for that refrigerant and cannot be used in R134a systems. R134a systems use either synthetic oil (PAG) YN-12 or Ester oil. Back to Top

3 LAWS OF AIR CONDITIONING
Everything has heat except at absolute zero (-460 degs. F)
LAW I: to refrigerate is to remove heat - the absence of heat is cold.
LAW II: heat is ready to pass to anything that has less heat - nothing can stop the flow, you can only slow it down
LAW III: if a change of state is to take place there must be a transfer of heat - If a liquid is to change to a gas it must take on heat.

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INSTALLING A COMPRESSOR

• Flush, with an approved solvent, to Clean the system
• Replace the Accumulator/Drier or Orifice tube
• Replace manifold sealing washers or O-rings
• Use a Vacuum Pump (20+ minutes) to remove moisture.
• Add the proper amount and type of oil. Check OEM spec
• Rotate compressor hub 12 times to oil the shaft seal
• Place a strong external airflow into the condenser
• Check OEM specifications for correct refrigerant charge
• Charge with VAPOR refrigerant and with A/C off.
• Do a leak test and check voltage at clutch coil
• Check belt tension and alignment
• Check system operation at 1500 RPM and mid-blower speed
• Use gauges to check the system pressures.

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HOW AUTO A/C WORKS
All matter has a certain amount of heat except at absolute zero (-460 degs F). Ice cubes feel cool to the touch, but actually it just has less heat than your hand. Heat is transferring from your hand to the ice cube. This is the principle behind how an A/C cools the air in a car. Heated air is circulated across a gas filled evaporator and is transferred to the refrigerant gas making the air less hot. The heat-laden refrigerant then is drawn into the compressor, is super heated by compression and forced through the condenser where the cooler outside air takes the heat from the refrigerant. Its next stop is the expansion device (TXV or Orifice tube), which meters refrigerant into the evaporator where it expands into a gas and it starts over again.

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LOW AIR FLOW

• The complaint: "it used to blow harder". Things to check are:
• Low blower motor voltage due to a poor ground
• Blower wheel loose on motor shaft
• Defective blower relay
• Air leak or obstruction in air duct system
• Air mode door directing some of the flow to the heater outlet
• Icing evaporator core due to condensation.
• Debris in evaporator housing that blocks air circulation.
• Obstruction at the air return

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CONNECTOR TERMINAL PROBLEMS
Electronic circuits are sensitive to voltage drops and operate in narrow voltage ranges. Many connectors have small spade or pin type connections and are engineered to have near zero resistance. If the connection is even slightly loose it will affect the voltage. What may seem to be a defective component could be a bad connector. The problem may be corrosion and careful brushing or using an electrical contact cleaner may cure it. Many OEM harness connectors are available as replacement parts.

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MOISTURE IN THE SYSTEM
Moisture causes internal icing that obstructs the orifice tube or expansion valve. This can create excessive high pressures and low cooling. The A/C system is a closed loop system so why does it need a Drier to remove moisture? Here's how moisture gets into the system. Refrigerant charged through service hoses not evacuated after being connected to the system will have air and moisture in them. Hoses left uncapped while replacing components allows moisture to enter. Refrigerant oil is hydroscopic (water absorbing like a sponge) and left uncapped will have moisture in it. Recycling machines with old filters will not remove moisture from incoming refrigerant. Condensation created when the Low side of the system gets cold and then warms up when the system is turned off is absorbed into the system through the hoses. Systems low on freon will pull moisture into the system when they go into a partial vacuum.

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EPA/SCAQMD CERTIFICATION
No need to wait for a group class. MACS on-line certification test and license. Cost $ 45.00 email: info@airpartsonline.com

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HEATER CONTROL VALVE - LITTLE OR NO HEAT
Most heating systems use a Heater Control Valve to regulate coolant flow into the heater core. The valve may be actuated by a cable, vacuum servomotor or electric solenoid. To check the valve: (1) determine if the valve is normally open or closed. (2) check valve position when not actuated, then switch the controls and monitor operation. A good valve opens and closes smoothly and completely. On vacuum operated valves you should check the vacuum hose for cracks. Controls the coolant flow to the heater core. On vehicles after 1971 the valve is normally open and closes only when the "max air" mode is selected. This assures maximum air draw off the evaporator core without heater overrun. Valves for vehicles prior to 1971 are normally closed valves that open when the heater is turned on

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THE BASIC A/C SYSTEMS - CCOT, TXV

ORIFICE TUBE SYSTEM
Orifice tube systems use an Accumulator located in the Low side of the system

EXPANSION VALVE SYSTEM
TXV systems use a Drier located in the High side of the system.

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CLUTCH CYCLING PRESSURE SWITCH
The clutch cycling switch for R134a vehicles has been calibrated for the slightly higher pressure of R134a. The threads, on the switch fitting, have been changed to metric to avoid connecting to a R12 system.

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ABOUT FANS & SHROUDS
FAN CLUTCH FAN: are designed to work only with a fluid coupling fan clutch. Do not attempt to alter a fan/fan clutch design by use of a spacer block or bolting the clutch together as doing so may increase the fan speed beyond the structural safety limit of the fan. HEAVY DUTY FIXED FANS: when used WITH A SHROUD it should be spaced to that half of he blade is within the shroud and half is outside of the shroud. If used WITHOUT A SHROUD it should be no closer than ¾ inch to the radiator and no further than 1-3/4 inch from the radiator.

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THERMOSTATIC FAN CLUTCH:
is an energy efficient, fan-driving fluid coupler. It is attached and driven by the water pump. When radiator heat load is high, the clutches bi-metal sensor activates and locks the clutch and the fan draws an increased volume of air over the engine.

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HOW MUCH ANTI-FREEZE (COOLANT)
A water and anti-freeze solution should be left in the vehicle radiator year-around. If it maintains its original color and is clear, it still has its rust inhibitors. The recommended mixture is 50-50 solution of water to anti-freeze. Below 30% anti-freeze does not provide enough corrosion protection and above 60% the anti-freeze protection "reverses" and there isn't enough water for effective heat transfer. NEVER use anti-freeze full strength.

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