AirComm Corporation Bell 412 Air Conditioner Instructions for Continued Airworthiness User Manual

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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F. Inspection of Air Conditioner Compressor Mount Assy. 
a. Visually inspect compressor mount of any signs of the following: 
1. Any cracks. 
2. Security of attaching hardware.  
3. Elongation of component mounting holes. 
4. Any loose rivets. 
 
G. Inspection of Air Conditioner Refrigerant Plumbing 
b. Visually inspect plumbing and fittings for any signs of the following: 
1. Refrigerant gas or oil leaks. 
2. Chaffing or excessive corrosion.  
3. Security of attaching hardware. 
 
H. Inspection of Compressor Drive system 
1. Cut the safety wire on the belt tensioning link assembly jam nuts and 
adjust the tensioning link assembly to loosen the compressor drive belt.  
2. Check the S-3532EC drive pulley for play relative to the tail rotor drive 
shaft, both in the direction of rotation as well as for lateral movement 
relative to the shaft, and inspect area around the base of the drive ring at 
the shaft for any buildup of metal dust/powder residue. 
3. If there is any detectable looseness, and/or if there is significant metal 
dust/powder residue present, refer to Section 8 for removal instructions 
to allow removal and further inspection to determine if the pulley or drive 
ring need to be replaced. 
4. If there is no detectable looseness, and no significant metal dust/powder 
residue present, re-tension the belt per Section 8. 
5. Check security and condition of all related fasteners. 
 
  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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CHAPTER 4 
LOCATION AND ACCESS 
 
1. LOCATION OF AIR CONDITIONER FEATURES 
 
Nomenclature Description of Location 
Air Conditioner Circuit Breaker Panel Located on the forward L/H side adjacent to 
the overhead circuit breaker panel. 
Air Conditioner Control Panel Located in the center pedestal. Exact location 
may vary depending on how the aircraft is 
equipped or configured. 
Relay Panel Assembly Located adjacent to the main transmission 
above the cabin headliner panel aircraft left.  
Forward (Cockpit) Evaporators Mounted in the chin-bubble just forward of the 
tail rotor control pedals. (One on the pilots and 
one on the co-pilots side respectively). 
Forward Evaporator Blower Assemblies Located in the nose compartment above the 
pilots & co-pilots chin-bubbles. 
Aft (Main Cabin) Evaporator Located on the main cabin roof under the 
forward transmission cowling. 
Condenser Assembly Located just forward of the main transmission 
on the cabin roof, and just aft of the aft 
evaporator assembly. 
Compressor Mounted on the aft side of the main 
transmission housing above the transmission 
input quill. 
Refrigerant Plumbing Routed from the cabin top, down through the 
main transmission pylon, to the belly of the 
aircraft, and forward to the nose area. 
 
2. LAYOUT OF AIR CONDITIONER SYSTEM 
 
 
Figure 4:  General Layout of Bell 412 Air Conditioning System  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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CHAPTER 5 
PLACARDS AND MARKINGS 
 
1. PLACARD AND MARKING INFORMATION 
 
System Charging Instruction Placard 
(Mounted to the R/H side of the condenser housing) 
 
NOTE 
Newer systems do not include the “BOULDER, COLORADO” annotation on the System 
Charging Instructions Placard. 
 
NOTE 
Systems shipped after June 1, 2015, include both “Polyester oil” and “Ultra PAG oil” in the 
annotation on the System Charging Instructions Placard. 
 
Compressor Placard 
(Mounted on top of the compressor body) 
 
 
Compressor Label 
(See page 27 for Safety Strap Installation details) 
    
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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CHAPTER 6 
SERVICING 
 
1. SAFETY PRECAUTIONS 
 
CAUTION 
Refrigeration servicing should be performed by qualified personnel only. 
 
The refrigerant used in the air conditioning system is the environmentally safe HFC 
R134a. This refrigerant is non-explosive, non-flammable, non- corrosive, has practically 
no odor, and is heavier than air. Although R134a is classified as a safe refrigerant, 
certain precautions must be observed to protect the parts involved and personnel 
working on the unit. 
 
Liquid R134a at normal atmospheric pressure and temperature evaporates so quickly 
that it tends to freeze anything that it contacts. Care must be taken to prevent any 
refrigerant from coming into contact with the skin, especially the eyes. 
 
WARNING 
Always wear safety goggles when servicing any part of the refrigerant system. Should any 
liquid refrigerant contact the skin or eyes, seek medical attention immediately even if the 
irritation ceases. 
 
WARNING 
To avoid explosion, never weld, use a flame-type leak detector, blow torch, solder, steam 
clean, bake on aircraft finish, or use excess amounts of heat on, or in the immediate area of 
the air conditioning system or refrigerant supply tank, while they are closed to the 
atmosphere. 
 
2. SERVICING INFORMATION 
 
This system should be serviced by QUALIFIED PERSONNEL ONLY. 
 
A. A list of suggested servicing equipment is provided later in this chapter. 
 
B. Connect the service manifold and vacuum pump to the service ports located on the right 
hand side of the cabin roof adjacent to the aft evaporator. 
 
C. Turn on the vacuum pump and open both valves to evacuate the system. When the 
pressure drops to 29.40 InHg (1.9 KgCm) moisture vaporizes and is drawn out of the 
system by the vacuum pump. Complete removal of moisture is important to prevent 
blockage of the expansion valves with ice. Leak check the system as described later in 
this chapter. 
 
NOTE 
Due to the drop in atmospheric pressure with an increase in altitude, the normal vacuum 
reading will drop approximately 1” InHg (1 KgCm) for each 1000 ft. (304.8 m) of altitude. 
 
D. After the system has been evacuated, turn off both manifold valves, and then turn the     
vacuum pump off. Allow a minimum of 1hour to check for vacuum leaks (if the system 
will not hold a vacuum, the system has a fitting leak). It may be necessary to charge the 
system with 1 or 2 lbs of refrigerant and conduct a leak check survey using an electronic 
leak detector.   
						

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CAUTION 
It is mandatory that the system be leak free to ensure trouble free operation.  Continuous 
operation of the system with insufficient charge will result in compressor damage. 
 
E. After the system is proven to be leak free, the system should be evacuated for a 
minimum of ½ hour before being charged with HFC R134a. 
 
F. Charging the system with 6.25 lbs. (2.8 Kg.) of R134a refrigerant is the most accurate 
method of charging. This should be accomplished using the suggested servicing 
equipment called out in this chapter. 
 
G. If a charging station is unavailable, the following procedure should be followed. Add an 
initial refrigerant charge of 2.0 lbs (0.9 Kg.) then continue to add refrigerant until the 
evaporator outlet air temperature and system suction pressures reach a minimum and 
subsequently start to increase. When adding the refrigerant after the initial charge, it 
should be done in increments of 0.2 lbs (89.6 gr.) and a minimum of 10 minutes elapsed 
time allowed before adding each additional 0.2 lbs. (89.6 gr.) refrigerant charge. The 
optimum charge occurs when evaporator outlet temperatures are at their lowest. Any 
additional refrigerant will cause the outlet air temperature to increase and system 
performance to be degraded.  
 
WARNING 
If the system is to be charged by operating the compressor it must be charged through the 
Lo pressure (suction) port only. 
Never open the Hi pressure (discharge) valve while the system is operating. 
 
H. Test-run the system after charging, to confirm the system is working properly. 
 
CAUTION 
When  reclaiming  refrigerant  be  sure  to  note  any  oil  that  is  removed  from  the  system  and 
replace  the  lost  oil  before  or  during  re-servicing.  Compressor  failure  is  possible  if  the  total 
system  oil-charge  is  not  maintained.  Excessive  system  oil  charge  will  reduce  cooling 
performance. 
 
Running  the  system  when  the  ambient  temperature  is  below  80 OF  will  present  unusual 
(low) suction and discharge pressures on system gauges. An overcharge condition is likely 
if  the  process  described  in  the  previous  paragraphs  A  through  G    is  followed  when  the 
ambient temperature is below 80 OF. Running the air conditioning system when the outside 
air  temperature  is  appreciably  colder  than  the  normal  design  operating  temperatures may 
result  in  damage  to  the  compressor.  The  following  guidelines  will  provide  means  to 
mitigate the chances of system damage. 
The following  assumes that  the  system  is  either a  freshly  installed  system  or  a  previously 
operated system with a newly installed compressor. 
 Ambient temperature above 80OF: 
If  the  system  was  charged  by  refrigerant  weight  utilizing  a  charging  station  and  the 
compressor  has  not  been  rotated  since  the  oil  and refrigerant  were  added,  then 
manually rotate the compressor shaft clockwise a minimum of 10 full revolutions prior to 
running  the  compressor.  A  socket  or  wrench  applied  to  the  shaft  nut  is  the  
						

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recommended  method.  Always  rotate  clockwise  to  insure  against  loosening  the 
compressor shaft nut. 
If  the  system  was  charged  per  Section 2 paragraph G of  this  Chapter  then  disregard 
manual rotation. 
Operate  system  normally,  check  for  evaporator  fan  operation  on  both  high  and  low 
speed settings. Insure that condenser fans are operating and airflow direction is correct.  
 Ambient temperature between 60 OF and 80 OF: 
At  these  ambient  temperatures  system  charging  is  to  be  accomplished  by  refrigerant 
weight.  The  method  mentioned  in  Chapter  6,  Section 2,  Paragraph G (above)  is  not 
applicable  at  these  condenser  inlet  temperatures.  It  is  recommended  that  the  aircraft 
heater  be  used  during  air  conditioner  system  testing  in  order  to  provide  a  heat  load  to 
the evaporators. 
Manually rotate the compressor shaft clockwise a minimum of 10 full revolutions prior to 
running  of  compressor.  A  socket  or  wrench  applied  to  the  shaft  nut  is  recommended 
method. Always rotate clockwise to insure against loosening the compressor shaft nut. 
Normal  suction  and  discharge  pressures  are  not  expected  under  these  conditions  and 
the  evaporators  may  be  cold  enough  to  cause  the  freeze  switch  to  activate  and  the 
bypass valve to open and close in a cyclic pattern. 
Even  though  the  bypass  valve  may  be  cycling  this  test  may  be  conducted  for  sufficient 
time  to  thoroughly  check  for  condenser  blower  and  fan  operation.  Check  for  evaporator 
fan  operation  on  both  high  and  low  speed  settings.  Insure  that  the  condenser  fan  is 
operating  and the  airflow  direction  is  correct.  Low  side  pressure  may  be  observed  to  be 
higher than expected when the bypass valve is open. 
 Ambient Temperatures between 60 OF and 32 OF: 
At  these  ambient  temperatures  system  charging  is  to  be  accomplished  by  refrigerant 
weight.  The  method  mentioned  in  Chapter  6,  Section 2,  Para. G (above)  is  not  allowed 
at  these  condenser  inlet  temperatures.  It  is  required  that  the  aircraft  heater,  or  another 
means of elevating the evaporator inlet air, be used during air conditioner system testing 
in order to provide a heat load to the evaporators. 
It  is  recommended  that  the  aircraft  be  warmed  in  a  heated  hangar  immediately  prior  to 
running the air conditioner test. Upon removing the aircraft from the heated environment 
the test should be started within ten minutes or as soon as practical. 
Manually rotate the compressor shaft clockwise a minimum of 10 full revolutions prior to 
running  of  compressor.  A  socket  or  wrench  applied  to  the  shaft  nut  is  recommended 
method. Always rotate clockwise to insure against loosening the compressor shaft nut. 
Normal  suction  and  discharge pressures  are  not  expected  under  these  conditions  and 
the  evaporators  may  be  cold  enough  to  cause  the  freeze  switch  to  activate  and  the 
bypass valve to open and close in a cyclic pattern.  
						

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At  these  ambient  temperatures  this  test  should  not  be  conducted  for more  than  15 
minutes.  Testing  the  evaporator  fan  operation  using  the  vent  position  prior  to  rolling  out 
of the hangar and prior to running the air conditioner system is recommended. Check for 
evaporator fan operation on both high and low speed settings. Insure that condenser fan 
is operating and the airflow direction is correct. 
 Ambient Temperature less than 32 OF: 
There  is  no  safe  way  to  operate  the  air  conditioning  compressor  with  ambient 
temperatures  below  32 OF.  Much  of  the system can  be  tested for  proper operation  even 
though the compressor cannot be run. 
Charge the system by refrigerant weight only. 
Manually  rotate  the  compressor  shaft  clockwise  a  minimum  of  10  full  revolutions.  A 
socket  or  wrench  applied  to  the  shaft  nut  is  recommended  method.  Always rotate 
clockwise to insure against loosening the compressor shaft nut. 
Temporarily disconnect the wire energizing the compressor clutch. 
Run  the  aircraft  and  turn  the  switch  to  air  conditioning.  Check  the  condenser  fan  for 
operation and correct direction of airflow. Check evaporator fans for airflow on both high 
and low settings. 
 
SYSTEM REFRIGERANT & OIL CHARGE 
 
System Description Refrigerant Charge Oil Charge 
412 Air Conditioner 6.25 lbs. 2.8 kg. 
9.0 oz. (new comp) 
 
7.0 oz. additional for 
412AC-102 kits 
 
266 ml. 
 
207 ml. 
 
 
 
 
3. LUBRICATION INFORMATION 
CAUTION 
This system may be serviced with either Polyolester (POE) or Double End Capped Polyalkylene 
Glycol (DEC PAG) oil.  Polyalkylene Glycol oil is preferred due to its superior lubricating properties 
and improved compressor service life.  There are several types of PAG available. Only the “Double 
End Capped” type is permissible in Air Comm Corporation air conditioning systems.  Double End 
Capped PAG oil is available from Air Comm Corporation in 8 ounce bottles (P/N ES94006-13).  
Mixing of POE and PAG is acceptable.  Disregard previous statements to the contrary. They 
referenced PAG oil that was not “Double End Capped”.  Current versions of compressors are 
designed to be operated using PAG oil.  Testing by Air Comm Corporation has shown that “Double 
End Capped” PAG is compatible with POE and can therefore be mixed. “Double End Capped” is a 
reference to the chemical structure of the molecule and not to the container. 
 
Do not use Mineral oil in this system with R134a refrigerant. Do not use any refrigerant oil other 
than Double End Capped Polyalkylene Glycol (also known as “ULTRA PAG”) or Polyolester (also 
POE). 
  
						

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Containers of DEC PAG or POE will absorb moisture if left open (hygroscopic). Keep 
containers tightly capped when not in use and keep all system components capped while 
servicing system. 
 
A. New Installations - The total system oil charge is 16.0 oz. (473 ml.) of R134a Ultra PAG 
Refrigerant Oil. The compressor is charged with 9.0 oz. (266 ml.) of oil at the factory, an 
additional 7.0 oz. (207 ml.) of oil must be added at the time of the system installation. 
This oil should be added to the compressor discharge line prior to system charging.  
These amounts are only applicable to new systems prior to any system operation.  A 
system that has been completely flushed may be treated as a new system for oil quantity. 
 
CAUTION 
Never add oil to the suction side of the system. 
 
The oil charge is continuously circulated by the refrigerant during the operation of the 
system. A quantity of oil is trapped by the compressor; it is possible to confirm the 
system oil charge after the system has operated for a minimum of ten minutes. This is 
done by checking the oil level in the compressor body. 
 
NOTE 
Maintaining the correct amount of refrigerant and refrigerant oil in the system is critical for 
ensuring the long life of the compressor. 
 
WARNING 
Discharge the system prior to checking the oil level. 
 
The oil level in the compressor should be checked as follows: 
 
a. Run the air conditioner compressor for 10 minutes with the engine at idle. 
 
b. Turn the air conditioner off, and SLOWLY recover all refrigerant from the system, 
 as not to lose any of the oil. 
 
c. Remove the filler plug from the top of the compressor body. 
 
d. Using a socket wrench, turn the compressor pulley retaining nut clockwise until 
 the counter weight on the face of the compressor is positioned as shown in  Figure 
5 below. 
 
e. Insert the oil dipstick up to the stop as shown in Figure 5 below. 
 
f. Remove dipstick and count the number of increments (notches) that are covered 
 by oil. The acceptable oil level for this compressor is a minimum of 8 increments. 
 
g. It may be necessary to add or subtract oil from the compressor to meet these 
 specifications. 
 
h. Inspect the filler plug O-ring for damage, cleanliness and proper seating, replace 
 if necessary. Torque to 11 – 15 ft. lbs. (15 – 20 N –m). 
  
						

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Figure 5:  Compressor Counter Weight and Dipstick 
 
B. Component  Replacement - Once  a  system  is  in  operation  the  lubrication  is  circulated 
through  the  system  along  with  the  refrigerant.  The  refrigerant  becomes  saturated  with 
the oil and carries it throughout the system, lubricating the compressor internal parts. No 
other  component  in  the  air  conditioning  system  requires  lubrication.  Excessive  oil  in  the 
system  causes  a  reduction  in  heat  transfer  and  will  result  in  poor  air  conditioning 
performance. 
 
C. When reclaiming refrigerant, be sure to measure and note any oil that is removed 
from  the  system.  If  a  measurement  is  not  available  use  1.5  oz.  as  the  estimated 
loss.  Replace any lost oil before or during re-servicing. Reduced compressor life 
will result if the total system oil charge is not maintained. 
 
D. Make  note  of  any  oil  lost  due  to  spillage  or  leaks  during  time  of  installation  or 
maintenance.  This  oil  must  be  replaced  before  the  air  conditioner  is  returned  to 
service. 
 
E. The  following  chart  may  be  used  to  calculate  the  amount  of  oil  to  be  added  in 
case a component is being replaced with a new part.  
 
Component Oil Amount 
Compressor See Instructions this 
section 
Evaporator 1.0 oz. per evaporator 
Condenser 1.5 oz. 
Receiver Drier 1.5 oz. 
Hose - Vapor 1.0 oz. per 10 foot 
Hose – Liquid 1.0 oz. per 20 foot 
 
P/N 90916   
						

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F. Compressor Replacement – To properly calculate the amount of oil required in 
the  replacement  compressor,  it  is  necessary  to  pour  the  oil  out  of  the  old 
compressor  into  a  clean container.  Drain  the  oil  out  of  the fill  plug  hole  and  then 
pour  oil  out  of  the  suction  and  discharge  ports  while  rotating  the  center  shaft 
clockwise.  Measure  the  total  amount  of  oil  removed  from  the  old  compressor. 
Add  ½  oz.  to  the  total  measured  to  account  for  unrecoverable  oil  in  the  old 
compressor.  This  total  is  what is  needed  in  the  new  compressor.  New 
compressors  come  from  Air  Comm  charged  with 9 oz.  (266.2  ml)  of  oil.  This 
should  be  adjusted  according  to  the  amount  of  oil  recovered  from  the  old 
compressor and any other components being replaced. The receiver drier should 
always  be  replaced  when  the  compressor  is  replaced  or  when  the  system  has 
been open for an appreciable time, which accounts for another 1.5 oz. of oil that 
should be added. 
 
G. Below are two different examples of compressor (and receiver drier) replacement 
for illustration: 
 
Example 1:  Draining the old compressor recovered 2.0 oz. of oil. Adding 0.5 oz. 
of  residual  unrecoverable  oil  in  the  compressor  gives  2.5  oz.  The  new 
receiver/drier requires an additional 1.5 oz., plus 1.5 oz. lost when the refrigerant 
was  evacuated  from  the  system.  So  the  total  oil  needed  in  the  replacement 
compressor  for  this  case  is  5.5  oz.  Since  the  new  compressor  comes  with 9 oz. 
of oil, remove the oil fill plug and pour out 3.5 oz. of oil. 
 
Example  2:  Evacuating  the  system  recovers  2  oz.  of  oil.  Draining  the  old 
compressor recovers 5 oz. of oil. Adding the ½ oz. of unrecoverable oil, plus 1.5 
oz.  for  the  new  receiver  drier  gives  a  total  of  9.0 oz.  needed.  The  compressor  is 
delivered  with 9 oz.  of  oil.  In  this  case, no additional oil  is  needed. If  oil  was 
needed,  it  could either  be  added  to  the  compressor,  or  to  the  plumbing 
downstream of the compressor. 
 
4. SYSTEM LEAK CHECK 
 
Identification and elimination of system fitting leaks is extremely important to ensure a 
trouble free operation of this system. 
 
A system which contains a partial charge of refrigerant can be leak tested with the aid of 
an electronic leak detector, and be recharged without evacuating the system.  
 
A new or empty system can be pressurized with nitrogen (70-80 psi) or R134a (50 psi) to 
conduct a leak survey. DO NOT USE COMPRESSED AIR. Compressed air will 
introduce moisture into the system, which will degrade the operation of the system. 
 
The preferred method is to use an electronic leak detector in conjunction with a small 
charge of R134a refrigerant. All checks done in this manner should be conducted with 
the air conditioner off. Since the refrigerant is heavier than air, leaks are most likely to be 
detected on the underside of hoses and fittings. Refrigerant will collect in low areas and 
provide erroneous leak detections. A stream of compressed air from a nozzle may be 
useful in clearing the area just prior to conducting a leak test. 
 
If the nitrogen method is used, it will be necessary to mix together a water-and-mild-soap 
solution. Each fitting or suspected leak area should be brushed with this soap solution 
and watched for evidence of bubbles formed by the escaping nitrogen.