Piper Navajo PA-31 Service Manual page 742

PIPER NAVAJO SERVICE MANUAL
(b) Check the torque indicated in step (a) with torque specified in the following
chart. Adjust belt tension accordingly.
Width of
Torque Indicated at
Belt
Condition
Alternator Pulley
3/8 inch
New
11 to 13 ft. lbs.
3/8 inch
Used
7 to 9 ft. lbs.
1/2 inch
New
13 to 15 ft. lbs.
1/2 inch
Used
9 to 11 ft. lbs.
NOTE:
See Paragraph 14-80 for Alternator Belt Tension when Freon Compressor is installed.
NOTE
The higher tension specified for a new belt is to compensate
for the initial stretch that takes place as soon as it is
operated. These higher tension values should not be applied
to belts which previously have been used.
2. Deflection Method: Belt tension may be checked by measuring the amount
of
deflection caused by a predetermined amount of tension; this is accomplished in the
following manner:
(a) Attach the hook of a small spring-scale to the belt at the approximate
mid-point between the ring gear support and the alternator.
(b) Pull on the scale until a reading of 14 pounds is obtained (10 pounds for
used belts).
(c) Measure the distance the belt has moved with the 10 to 14 pound load
applied. The distance (deflection) should be 5/16 inch. If less than 5/16
inch, the belt is too tight.
3. Note that the belt tension of the belt is adjusted by means of an idler pulley.
c. Check pulley alignment by one of the following methods:
1. Visually check the alignment of the compressor pulley with the crankshaft
pulley, there must not be any misalignment.
2. A half inch rod about 18 inches long can also be used to check pulley alignment
before installing the drive belt, by laying the rod in the pulley grooves and
make sure that
rod falls squarely in the two pulley grooves.
NOTE
Assure that the belt is properly aligned. Misalignment
produces rapid belt wear.
Reissued: 10/12/79
ELECTRICAL SYSTEM
4C16