Sterling MS - Manual (Page 25)

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VII. TROUBLESHOOTING
For troubleshooting of the duct furnace, refer to the Separated Combustion Indoor Gas-Fired Duct Furnace Installation
and Service Manual. For Evaporative Cooler/Cooling Coil equipped units, refer to these specifi c manuals for additional
troubleshooting guides.
For additional troubleshooting, see following Troubleshooting Guide.
TROUBLESHOOTING GUIDE
AIR BLOWER
PROBLEM PROBABLE CAUSE SOLUTION
1. Noise Blower Wheel Hitting Scroll Side a. Blower Wheel not centered in blower housing.
b. Damaged blower housing.
c. Damaged blower wheel.
d. Shaft loose in blower bearing.
e. Blower Wheel loose on shaft.
f. Blower bearing loose in bearing support.
Blower Wheel Hitting Cutoff a. Cutoff not secure in blower housing.
b. Cutoff damaged.
c. Cutoff improperly positioned.
Drive a. Pulley not tight on shaft (motor and/or blower
wheel).
b. Belts too loose. Adjust for belt stretching after 48
hours of operation.
c. Belts too tight.
d. Belts wrong cross section.
e. Belts not matched in length on multi-belt drive.
f. Variable pitch pulleys not adjusted so each pulley
has same pitch diameter (multi-belt drives).
g. Misaligned pulleys.
h. Belts worn.
i. Motor or motor base loose.
j. Belts oily or dirty.
k. Improper drive selection.
Bearing a. Defective bearing.
b. Needs lubrication.
c. Loose on bearing support.
d. Loose on shaft.
e. Seals misaligned.
f. Foreign material in bearing.
g. Worn bearing.
h. Fretting corrosion between inner race and shaft.
Shaft Seal Squeal a. Needs lubrication.
b. Misaligned.