Craftsman 921.164780 Owner's Manual page 33

Troubleshooting Guide
The air compressor should be turned off and unplugged from the power source before any
maintenance is performed as well as the air bled from the tank and the unit allowed time to cool.
Personal injuries could occur from moving parts, electrical sources, compressed air, or hot surfaces.
PROBLEM
Air leaks at the check valve
or at the pressure relief valve.
Air leaks between head and
cylinder.
Air leak from safety valve.
Pressure reading on the
regulated pressure gauge
drops when an accessory is
used.
Excessive tank pressure.
Motor will not start.
Excessive moisture in the
discharge air.
Air leaks from the tank body
or tank welds.
POSSIBLE CORRECTION
A defective check valve results in a constant air leak at the pressure relief valve
when there is pressure in the tank and the compressor is shut off. Drain the tank,
then remove and clean or replace the check valve.
Be sure of proper torque on head bolts. If leak remains, contact a service technician.
Operate the safety valve manually by pulling on the ring. If the valve continues to
leak when in the closed position, it should be replaced.
If there is an excessive amount of pressure drop when the accessory is used,
replace the regulator.
Adjust the regulated pressure under flow conditions (while accessory is being used).
It is normal for the gauge to show minimal pressure loss during initial use of the
tool.
Move the Auto/Off lever to the Off position. If the unit doesn't shut off,
unplug it from the power source and contact a service technician.
Make sure power cord is plugged in and the switch is on. Inspect for the proper size
fuse in your circuit box. If the fuse was tripped, reset it and restart the unit. If
repeated tripping occurs, replace the check valve or contact a service technician.
Remove the water in the tank by draining after each use. High humidity
environments will cause excessive condensation. Utilize water filters on your air
line.
m
Water condensation is not caused by compressor malfunction. Be sure the
compressor's air output is greater than your tool's air consumption rate.
Never drill into, weld or otherwise modify the air tank or it will weaken. The tank can
rupture or explode. Compressor cannot be repaired. Discontinue use of the air
compressor.