22.
Place the blower housing in position on the jacket assembly and secure it by installing the four screws, if removed at disassembly. This operation is easier if the screws are started into their threads and the blower housing rotated into place allowing the screws to enter the notched openings in edge of blower housing. Tighten all screws securely.

23.
Install the elbow adapter with the screw.

24.
After heater is installed in the aircraft and the fuel line is connected, install the upper fuel shroud box with the screws.  Ascertain that the grommet is installed.

REASSEMBLY OF COMBUSTION AIR BLOWER ASSEMBLY. (Refer to Figure 21-19.)
1.  
Place the spacer over the end of the motor shaft and attach the motor assembly to the inner housing with the two self-locking nuts, flat washers and lock washers.

2.  
Slide the blower wheel on the motor shaft and tighten the set screw lightly against the flat portion of the motor shaft.

3.  
Place the outer blower housing in position on the inner housing and install screws.

4.  
Attach the radio/noise filter at the point shown with the screw.  The motor ground lead terminal can be grounded to the motor support bracket.

5.  
Loosen the Allen-head set screw in the blower wheel and shift the wheel on the motor shaft until it is near the inlet in the blower housing.  Tighten the set screw securely. The blower wheel should just clear the inlet flange when rotated at full RPM. Spin the blower wheel by hand for clearance check; then apply proper voltage to run motor and recheck for proper clearance.

6.  
Attach the blower inlet adapter to blower housing with screw.

21-40-00 Page 21-49 Revised: February 28, 2002

21-40-00 Page 21-50 Revised: February 28, 2002
1I24
TEST PROCEDURE.
GENERAL INFORMATION.
A test of all components should have been made after overhaul to insure proper operation.  Some shops may not have complete testing facilities for measuring airflows, pressure drops, and other factors which would be accomplished in a laboratory-type test. If such a test cannot be made, install the heater and check operation on the ground and in the air to determine if operation is normal. In shops where complete test equipment is available and a complete functional test can be performed, the test routine described in subsequent paragraphs should be made.
EQUIPMENT REQUIRED. (Refer to Figure 21-20.)
1.  
An improvised stand to hold the heater during test.  The heater should be located far enough away from any combustible material or atmosphere to avoid hazard.  A location should be chosen where exhaust can be dispelled. Do not add an excessive extension to the heater exhaust.

2.  
A source of fuel capable of being regulated at seven psi.

3.  
The combustion air blower to be used with the heater should be used for the test.

4.  
A 12 volt current supply which may be a DC generator with a rheostat, ammeter, and voltmeter in the line to control and indicate the current draw and voltage output.

5.  
Two water manometers (zero to 5.0 inch water column) for measuring the pressure in the ventilating air duct and in the combustion air stream.

6.  
A piece of duct to be attached to the downstream end of the heater.  It should have a minimum length of 24 inches and the same diameter as the heater being tested. A 2.25 inch diameter orifice should be centrally located at the outlet end. An aperture should be provided for the thermometer and duct switch and a static tap should be attached as shown in Figure 21-20.

7.  
A thermometer with 500° F scale.

8.  
A fuel-pressure gauge.

9.  
A controlled source of compressed air for final leakage test.

OPERATIONAL TEST (ON TEST BENCH). (Refer to Figures 21-20 and 21-21)
1.  
Connect the heater to the test setup as shown in Figure 21-20. Make sure the combustion air blower is mounted securely and that the heater is clamped to its supporting stand.

2.  
Insert the duct switch in the sheet metal extension tube at the location shown in Figure 21-20.

3.  
Connect components and heater as outlined in the wiring connection diagram, Figure 21-21.  The power supply switch should be open.

4.  
Connect the power source to the heater.

5.  
Disconnect wire lead from terminal No. 3 on the heater side of heater terminal strip to prevent the heater from lighting and close the power source switch to check operation of blowers.  The combustion air blower and ventilating air blower should operate at full speed with no blower wheel interference.  If either blower fails to run, locate and correct the trouble before proceeding with the test.
　
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