TROUBLESHOOTING GUIDE
SYMPTOM
Excessive noise in operation
Milky oil in oil reservoir
Excessive oil consumption or oil
in air lines
Water in discharge air
Air blowing out of inlet
Insufficient pressure
Tank does not hold pressure
when compressor is off and
shutoff valve is closed
Excessive belt wear. (Light dust
from start is normal. Worn belts
separate at layers)
Tank pressure builds slowly
Tank pressure builds up quickly
on compressor
ASME safety valve pops open
while compressor is running
Pressure switch continuously
blows air out the unloader valve
Pressure switch unloader valve
does not release air when the
unit shuts off
POSSIBLE CAUSE(S)
1. Loose pulley, flywheel, belt, beltguard,
etc
2. Lack of oil in crankcase
3. Compressor floor mounting loose
4. Malfunctioning check valve
5. Unit not on vibration pads
Water condensing in crankcase due to high
humidity
1. Be sure there is a problem
2. Restricted air intake
3. Wrong oil viscosity
4. Worn piston rings
5. Oil leaks
6. Scored cylinder
1. Excessive water in tank
2. Hot, humid weather
1. Broken first stage inlet valve (two-
stage unit)
2. Broken inlet valve (single stage unit)
1. Air demand too high
2. Leaks or restrictions in hoses or piping 2. Check for leaks or restriction in hose or piping
3. Slipping belts
1. Worn check valve
2. Check all connections and fittings for
tightness
3. Check tank for cracks or pin holes
1. Pulley out of alignment
2. Belts too tight or too loose
1. Dirty air filter
2. Blown cylinder head gasket
3. Worn/broken intake/discharge valves
4. Air leaks
Excessive water in tank
1. Wrong pressure switch setting
2. Malfunctioning ASME safety valve
3. Pressure switch contacts welded
Malfunctioning check valve
Malfunctioning unloader valve on pressure
switch
CORRECTIVE ACTION
1. Tighten
2. Check for damage to bearings, replenish oil
3. Shim to level and tighten or place on islolator pads
4. Replace check valve
5. Install vibration pads under compressor feet
Pipe air intake to less humid air source. Run pump
continuously for one hour
1. Diagnose oil contamination problems by testing the
discharge air or measuring oil consumption from the
crankcase
2. Clean or replace air filter
3. Drain oil. Refill with oil of proper viscosity
4. Replace rings
5. Tighten bolts, replace gaskets or o-rings
6. Replace cylinder
1. Drain tank
2. Purchase dryer
1. Replace valve assembly
2. Replace valve assembly
1. Limit air usage
3. Tighten belts
1. Replace check valve
2. Tighten
3. Replace tank. Never repair a damaged tank
1. Realign motor pulley
2. Adjust tension
1. Clean or replace filter element
2. Install new gasket
3. Install new valve plate assembly
4. Tighten joints
Drain tank, check speed. See Performance table
1. Adjust to lower pressure 140 psi for single stage unit
(See Operation)
2. Replace ASME safety valve
3. Replace pressure switch
Replace the check valve if the unloader valve bleeds off
constantly
Replace the pressure switch if the unit does not hiss for a
short period of time when the unit shuts off
12
Do not disassemble check valve with
air in tank