99M90
21-40-01
Page: 8-3
Rev. New
Issued: May 9, 2012
I-Series Combustion Heater
Owners Manual
8.4
Combustion Air Blower Maintenance: (Refer to Figure 8.1 & 8.2)
A. Removal:
1.
Remove access panels if necessary to reach the combustion air blower assembly.
2.
Disconnect the electrical cable connection at the most convenient location.
3.
Disconnect the air tube between the blower and combustion air adapter on the heater.
If the combustion air blower inlet adapter is used, disconnect it from the inlet tubing. This
will depend upon the type of connecting tubing used and the method of attachment.
4.
Disengage the clamp that secures the combustion air blower and remove the blower
motor assembly. It will usually be possible to remove the assembly by loosening the
clamp and sliding the motor out of the clamp. In some installations it is easier to remove
blower and mounting bracket from the aircraft.
B. Brush removal & Installation:
1.
Remove the brush cap at one of the brush locations. Note position of brush inside the
guide and carefully lift the brush and brush spring out of the guide. Be sure to note
the brush orientation in the guide so that it can be re-installed in the same position if
inspection of the brush shows replacement is not required. On Motor Part No's.
27D39 and 34D30 it is necessary to remove motor case to replace brushes.
2.
Inspect the brush for wear. If brushes are worn to a length of 3/16" or less they must
be replaced. If this limit has not been reached, the brushes may be reinstalled in the
orientation noted in step 1.
3.
Looking through the brush guide, inspect the commutator, which should be smooth and
medium brown to dark brown in color. Remove all dust from commutator with
compressed air. If the commutator is grooved in, the brush track, gouged, scored or
shows signs of having burned spots, replace the complete motor assembly. If the
commutator is in good condition, install new motor brushes, and tighten brush caps into
place. Make sure each brush is oriented so that the curved end fits the curvature of
the commutator.
4.
Install brushes in the reverse order of removal.
5.
After installing new brushes, it is advisable to “run in” the brushes as follows:
Connect the motor to a controlled voltage supply (rheostat in a 28 volt DC line for 28
volt motor and a 12 volt line for 12 volt motor). Operate the motor at approximately
1/2 its normal speed for the first hour, then gradually increase the speed until it is
rotating at approximately normal speed. Continue the “run in” operation for at least
two hours to properly seat the brushes before installing the blower in the aircraft.
