INSPECT COMBINING TRANSMISSION FAN ASSEMBLY AND FAN DRIVE
INSPECT FAN ASSEMBLY
Turn fan shaft (8) by hand several turns. There
shall be no binding or noise. Look for evidence
of overheating, discoloration, paint blistering, or
vane tip contact on housing (9).
Try to rotate one impeller (10 or 11) with respect
to the other by securing one impeller to the
housing and rotating the other impeller by hand.
No rotational looseness is allowed.
Try to move shaft (8) up and down. Free play
shall not exceed 0.010 inch.
Measure the gap between the vanes of impeller
(10 or 11) and the inside of housing (98) at two
places as follows:
Place two index marks 180º apart on the
housing flange. Use a marking pencil (E271).
Also, index two impeller vanes approximately
Move the impeller radially as far as possible
toward one index mark on the housing.
Holding impeller in place, measure gap
between indexed vane tips and the inside of
the housing at each index mark. Gaps shall
be 0.015 to 0.030 inch.
Move the impeller radially as far as possible in
the opposite direction toward the other index
mark. Holding the impeller in place, measure
the gap between the same vanes and the
inside of the housing at each index mark.
Subtract the gaps measured in step b from
the gaps measured at the same index marks
in step c. The largest of these two values
indicates the radial play of the impeller and
shall not exceed 0.004 inch.
If radial play is less than 0.004 inch, repeat
steps a thru d for the other impeller.
Examine impellers (10 and 11) for damage:
In area A, dents, gouges, and chips to 0.010
inch are allowed.
In area B, dents, gouges, and chips to 0.030
inch are allowed.
Uniform erosion is allowed over the entire
blade. Such erosion is seen as a smooth
transition from silver (magnesium) to tan
(anodize) to yellow (primer) to black (topcoat).