6--3
T--311
Change 07/09
Clearance Zone Identification
Clearance at Mid Span
Figure 6-5 Belt Clearance Requirements
6.3.3 Pulley Alignment
Correct belt alignment is essential for alternator and
compressor belt life. The center line of all pulleys related
to compressor or alternator drive must be within 1/3
degree of true center. Refer to Figure 6-6 for
approximate measurements, and keep in mind, these
are maximum values. You should try to attain perfect
alignment whenever possible to maximize component
and belt life.
Maximum allowable run-out for Poly ”V” belts is 1/8 inch.
Maximum allowable run-out for Standard ”V” belts is 1/4
inch.
Methods and tools used in determining proper
alignment are illustrated in Figure 6-6 and Figure 6-7. A
high quality straight edge is a necessity, your eye is not
an acceptable method of determining proper belt
alignment. Precision Tools make a line of straight edges
that would be suitable for compressor and alternator
alignment purposes. Other alternatives are available
please contact the Carrier Transport Air Conditioning
Technical Service Hot Line (1--800-450-2211) with any
questions or comments. All mounting brackets should
allow for minor belt center line adjustments.
Parallel
Misalignment
Angular
Misalignment
Figure 6-6 Belt Misalignment
Parallel adjustment is designed into a mount for final
alignment during the installation process. This is
necessary due to manufacturing and engine tolerances
as well as multiple applications and different engine
options available. Parallel misalignment is corrected by
moving the driven pulley (alternator or compressor) into
alignment with the drive pulley. This can be done using
several methods. Spacing the component forward or
rearward by adding or removing spacers is the most
popular method used to achieve proper alignment.
Other methods such as sliding the component forward
or rearwards using slide plates and/or slots in the main
weldment are also used.
Angular misalignment is often caused by tolerances in
several pieces, such as hardware to mounting holes and
plates to components. This could also be from a poorly
built
design and/or
installed bracket.
Excessive
modifications such as grinding or drilling holes to a
larger diameter to apply/install a kit should be avoided
when
possible.
Minimizing
tolerances
must
be
considered during the design process to minimize this
problem.
Angular
misalignment
is
corrected
by
loosening the mounting hardware, adjusting the
compressor to the proper angle and retightening the
mounting hardware.
Correct
Incorrect
Figure 6-7 Straight-Edge Application
Proper use of a straight edge is illustrated in Figure 6-7 .
Never use a straight edge on the wide/flat side, as they
are not accurate. The thin edge is a straight surface and
the only accurate surface. The straight edge must be
flush across the face of the pulley. Then, to measure the
alignment, lower the other end down to the driven
pulley(s). Adjustments are made based on results of the
aforementioned. Note that the pulley rim width must be