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. Replace Item 48, 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 Disas-
sembly” 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 Disas-
sembly” 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 “Shaft
Balancer and Spindle Disassembly” and “Spindle
Bearings, AirSHIELD™ and Shaft Balancer As-
sembly”.
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 dam-
aged parts. See Steps 2 and 3 in “Housing Disas-
sembly” 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
“Service Manual”)
Worn or broken Rear or Front Motor
Bearing(s)
Replace the worn or broken Bearings. See “Motor
Disassembly” and “Motor Assembly”.
For central vacuum machines it is possible
to have too much vacuum while sanding
on a flat surface causing the pad to stick
to the sanding surface.
For CV machines reduce vacuum through the
vacuum system.
Troubleshooting Guide
Note: All Sections referred to under “Solution” are located at the end of the manual in “Service Instructions”
