Piper PA-28-161, Maintenance Manual

Page: 294 / 1104

PIPER AIRCRAFT, INC.
PA-28-161, WARRIOR III
MAINTENANCE MANUAL
2E4
24-30-00 PAGE 12
Nov 30/06
E. Alternator Belt Tension Adjustment
CAUTION: AN IMPROPERL\Y TENSIONED BELT WILL WEAR RAPIDLY, SLIP, AND REDUCE
ALTERNATOR OUTPUT. BELT MUST BE CHECKED FOR PROPER TENSION AT
INSTALLATION, AFTER FIRST 25 HOURS OPERATION, AND EACH 100 HOURS
THEREAFTER.
There are three acceptable methods of checking alternator belt tension: the torque method, the
deflection method,and using a belt tension gauge.
(1) Torque Method: This method of checking belt tension consists of measuring torque required to
slip the belt at the small pulley as follows:
NOTE: Chrysler alternators do not have a nut on the shaft, and therefore, cannot be checked
by this method.
(a) Apply a torque indicating wrench to the nut attaching pulley to alternator and turn in a
clockwise direction. Observe torque shown on wrench at the instant the pulley slips.
(b) Check torque in Step a with torque specified in the following Chart 3. Adjust belt to proper
tension.
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 have previously been used.
(2) Deflection Method: Check belt tension by measuring the amount of deflection caused by a
predetermined amount of tension as follows:
(a) Attach the hook of a small spring-scale to the belt at the mid-point between rear gear
support and alternator.
(b) Pull scale until it reads 14 pounds. (10 pounds for used belts.)
(c) Measure the distance the belt moved with the 10 or 14 pound load. The distance
(deflection) must be 5/16 inch. If less than 5/16 inch, belt is too tight.
(3) Use a belt tension gauge such as the Burroughs deluxe model or equivalent.
(a) Attach gauge over the belt per manufacturer’s instructions.
(b) Quickly release handle and read tension.
(c) Repeat steps a and b several times to eliminate the possibility of an inaccurate reading.
NOTE: Slight variations in readings taken at different locations on the belt are normal.
(d) If a new belt is installed, set tension 25 percent above operating range to allow for stretch
that will occur as soon as belt is operated.
(4) Complete alternator belt tension adjustment, and tighten alternator pivot bolts to a torque of
225 to 255 inch-pounds.
CHART 3
ALTERNATOR BELT TENSION
Belt Width Belt Condition Torque Indicated
(at Alternator Pulley)
1/2 inch New 13 to 15 ft.-lb.
1/2 inch Used 9 to 11 ft.-lb.