7
Symptom
Possible Cause
Solution
Low Power and/or Low Free
Speed
Insufficient Air Pressure
Check air line pressure at the Inlet of the Sander
while the tool is running at free speed. It must be 6.2
Bar (90 psig/620 kPa).
Clogged Muffler(s)
See the “Housing Disassembly” section for Muffler
removal. The Item 20 Muffler can be back flushed
with a clean, suitable cleaning solution until all
contaminates and obstructions have been removed. If
the Muffler can not be properly cleaned then replace
it. Replace Item 21, Muffler Insert (See the “Housing
Assembly” Section).
Plugged Inlet Screen
Clean the Inlet Screen with a clean, suitable cleaning
solution. If Screen does not come clean replace it.
One or more Worn or Broken Vanes
Install a complete set of new Vanes (all vanes must
be replaced for proper operation). Coat all vanes with
quality pneumatic tool oil. See “Motor Disassembly”
and “Motor Assembly”.
Internal air leakage in the Motor Housing
indicated by higher than normal air con-
sumption and lower than normal speed.
Check for proper Motor alignment and Lock Ring
engagement. Check for damaged O-Ring in Lock
Ring groove. Remove Motor Assembly and Re-Install
the Motor Assembly. See “Motor Disassembly” and
“Motor Assembly”.
Motor Parts Worn
Overhaul Motor. Contact authorized Mirka Service
Center.
Worn or broken Spindle Bearings
Replace the worn or broken Bearings. See “Mini Ran-
dom Orbital Head Disassembly” and “Mini Random
Orbital Head Assembly”.
Air leakage through the Speed
Control and/or Valve Stem.
Dirty, broken or bent Valve Spring, Valve
or Valve Seat.
Disassemble, inspect and replace wore or damaged
parts. See Steps 2 and 3 in “Housing Disassembly”
and Steps 2 and 3 in “Housing Assembly”.
Vibration/Rough Operation
Incorrect Pad
Only use Pad Sizes and Weights designed for the
machine.
Addition of interface pad or other material
Only use abrasive and/or interface designed for the
machine. Do not attach anything to the Sanders Pad
face that was not specifically designed to be used
with the Pad and Sander.
Improper lubrication or buildup of foreign
debris.
Disassemble the Sander and clean in a suitable
cleaning solution. Assemble the Sander. (See “Ser-
vice Manual”)
Worn or broken Rear or Front Motor
Bearing(s)
Replace the worn or broken Bearings. See “Motor
Disassembly” and “Motor Assembly”.
Note: (All Sections referred to under “Solution” are located at the end of the manual in “Service Instructions”)
Troubleshooting Guide
