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PROBLEM
Customer reports
frequent Thermal
Protection trips, indicated
by Continuous Red LED
When grinder is plugged
in green indicator LED is
not illuminated and tool
fails to start when
switched on. (Zero
rotation of output
spindle).
Revision 2 – May 28, 2019
ITEM
CAUSE & ANALYSIS
Motor Damage / Short: Contamination can
cause abrasion of the copper coils. If the
coils are damaged and contamination builds
up on the coils they can short to themselves
resulting in higher temperatures of the stator
and thermal trips. With tool unplugged
12
remove 4 gear case to field case attachment
screws and remove rotor and gear case
assembly. Inspect coils for heavy
contamination build up, burnt coils or wires.
See Figure 3 for example of a shorted coil.
Rotor Damage or Demag: The rotor has four
high strength magnets that can lose their
magnetism under severe conditions such as:
operating the tool with a shorted stator, heavy
use that often results in thermal shutdowns or
in some cases a module short.
Generally, if the magnets are degraded they
are severely degraded and can easily be
13
identified. If you place a small screwdriver or
piece of steel against the rotor the attraction
from each of the four magnets should be
strong along the full length of the rotor /
magnet segment. Generally, when a rotor has
demag there is an obvious lack of
magnetization over a large area of the rotor.
See Figure 4 for location & orientation of
magnets.
Cordset damage: Unplug tool and inspect
cordset & plug for damage. Remove handle
14
covers and check for continuity between
terminal lugs and plug for each conductor.
Contamination at Hall or Switch connection
prevents Module from powering up: With tool
unplugged remove handle covers and inspect
white glue coverage for any exposed areas
that could allow contamination to enter the
connection area. When in doubt thoroughly
remove external white glue from the
connections. Gently pry out the Hall (5 wire) &
15
Switch (3 wire) connectors and inspect the
socket and plug for contamination. Use
compressed air to clean contamination from
the connections. Reinstall the connectors
and temporarily install the handle covers.
Plug tool back in and check for Green LED
and that tool starts. See Figure 1 for proper
area to pry off top Handle Cover.
REMEDY
Replace Stator and check rotor
for Demag.
Replace Rotor & Stator.
If module is failed replace it
also.
With tool unplugged replace
cordset and liberally apply white
glue to cover and protect the
connection posts from
contamination.
Unplug tool, remove handle
covers to access hall and
switch connections on module.
Remove excessive glue and
gently unplug switch (3 wire)
and Hall board (5 wire)
connections. Use compressed
air to remove contamination
from connector and socket.
Reinstall connectors and
limberly apply white glue to seal
connections and cordset
attachment posts to seal from
contamination. See Figure 2 for
proper application of white glue.
Reinstall handle covers and
lanyard attachment point.
Page 5 of 6
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