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

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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CHAPTER 8 
TROUBLESHOOTING 
 
1. SYSTEM TROUBLESHOOTING 
 
Prior to troubleshooting a defective system, it is advisable to conduct a visual inspection for 
general condition, and obvious signs of damage or failure.  
 
The following matrix lists the easiest checks, and the most likely problems. 
 
Problem Probable Cause Solution 
System not Cooling 
(Evaporator blowers still 
operating) 
a. System is low or empty of 
refrigerant. 
 
a. Evacuate the system, 
determine the origin of the 
refrigerant leak, and re-
charge the system as 
prescribed in chapter 6. 
b. Moisture or air in the system. b. Evacuate the system, 
Replace the receiver / drier, 
and place the system under 
a vacuum for a minimum of 
30 minutes before recharging 
the system. ¹ 
c. Compressor  c. If the compressor has failed, 
it must be replaced. ¹ 
d. Compressor drive belt  d. If the compressor drive 
belt(s) have failed they will 
need to be replaced. Replace 
and adjust compressor drive 
belt(s) as prescribed in 
chapter 7. ¹ 
e. By-pass valve  e. Check to ensure the 
temperature control knob on 
the A/C control panel in the 
cockpit is in the full cold 
position, and the temperature 
control circuit breaker has 
not tripped. If the valve 
remains open (by-passing 
refrigerant) the valve will 
need replacement. ¹ 
f. Condenser blower motor(s) & 
fan assemblies  
      (Part No. ES73131) 
f. Check to ensure the 
condenser blower motor(s) 
and fan assemblies are 
receiving power, and the 
circuit breakers have not 
tripped. If the blowers still do 
not function they may have 
failed internally and must be 
replaced as shown in chapter 
7. ¹ 
System not cooling 
(Evaporator blowers not 
operating) 
g. Air conditioner control circuit 
breaker tripped. 
g. Reset circuit breaker, if 
breaker will not reset, check 
for short in circuit. 
h. Forward or Aft evaporator 
blower circuit breaker 
tripped. 
h. Reset circuit breaker, if 
breaker will not reset, check 
for short in circuit. 
  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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(System troubleshooting continued) 
 
Problem Probable Cause Solution 
System not cooling 
(Evaporator blowers not 
operating) 
i. Forward and aft evaporator 
blower motor(s)   
 
     
i. Check for power to the 
motor(s), and for the free 
movement of the blower 
wheel. If the motor shaft 
does not turn smoothly the 
motor must be replaced. ¹ 
Loss of cooling limited to one 
evaporator. 
j. Expansion valve malfunction. j. If cooling is lost in only one of 
the evaporators, and the 
blowers continue to function, 
is most likely a blockage at 
the expansion valve orifice. 
This is most often caused by 
moisture in the system 
forming ice as the refrigerant 
passes through the valve. 
Evacuating the system and 
changing the receiver drier 
should cure this problem. If 
this problem occurs at only 
one evaporator, the problem 
could be caused by dirt or 
other contaminant blocking 
the valve. In extreme cases 
of blockage the expansion 
valve may have to be 
replaced. ¹ 
Water in chin bubble area of 
forward evaporators 
k. Leak in evaporator or 
evaporator drainage system. 
k. If water is noted in the chin 
bubble area near the forward 
evaporators. This is normally 
caused by a loose, cracked, 
plugged, or disconnected 
drain line. 
Water (Condensate) in the 
area of the aft evaporator. 
l. Aft evaporator drainage 
system. 
l. If water is noted coming from 
the main cabin outlets, or the 
aft evaporator return air duct, 
the drain line is most likely 
plugged. A small amount of 
compressed air on the end of 
the drain line will usually 
dislodge any obstruction. 
 
(1 Contact Air Comm Corporation Service Department for current pricing and availability of 
replacement components and parts). 
 
 
 
 
 
 
 
 
 
  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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Figure 13:  REFRIGERANT PLUMBING SCHEMATIC 
   
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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(Refrigerant plumbing schematic continued) 
 
 
 
Figure 14:  Refrigerant plumbing schematic (continued) 
  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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Figure 15:  412AC-808 ELECTRICAL SCHEMATIC 
  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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Figure 16:  412AC-808 electrical schematic (continued)  
						

							AIR CONDITIONER SERVICE MANUAL 412AC-208M 
 
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APPENDIX A 
Weight and Balance Information 
 
 
 
Weight breakdown – Bell 412 Series Air Conditioner System: 
 Ref. Dwg. 412AC-102-1 / -2 
 
 
Item Wt. (lbs) ArmX (in) MX (in-lb.) 
Total (-1 or -2 
installation) 
174.90 104.4 18,260