48
Chapter 4
WARNING!
To avoid electric shock, electrocu-
tion, and terminal venting with ignition do not
energize a compressor that has a ground fault.
If a ground fault exists, keep the power off and
replace the compressor. See “System Cleanup and
Compressor Replacement After Compressor Fail-
ure” on pages 104-107. If the compressor is not
replaced immediately, mark and red tag the com-
pressor to indicate there is a ground fault. Do not
reconnect the power leads. Tape and insulate each
power lead separately.
If a ground fault does not exist, leave the power off
and all external components disconnected from the
terminal pins. Check for continuity and proper
resistance using the procedure in Section B.
B. Checking for Continuity and Proper
Resistance
If no ground fault has been detected using the pro-
cedures in Section A, determine whether there is an
open or short circuit in the motor windings or if the
heater element of the thermal protector is open. Use
the procedure in Table 4-1 to check single- and 3-
phase motors.
Why use a megger or Hi-Pot?
Tecumseh Products Company recom-
mends checking for a ground fault only
with a megger or Hi-Pot. A conventional
ohmmeter will not reliably detect a
ground fault under certain circum-
stances.
A megger is a special type of ohmmeter
that is capable of measuring very high
resistances by using high voltages. A Hi-
Pot is a device that uses high voltages to
measure the flow of current across the
insulation. Unlike an ohmmeter, even
one that can measure millions of ohms,
a megger or a Hi-Pot can detect a break-
down in motor winding insulation before
the motor fails
.
WARNING!
To reduce
the risk of electrocution, always follow
the manufacturers’ procedures and
safety rules.
Figure 4-1.
Top: Amprobe megohmmeter (commonly referred to as a “megger”). (Photo courtesy of
Amprobe.) Bottom: A Slaughter Hi-Potential Ground Tester (commonly referred to as a “Hi-
Pot”). (Photo courtesy of Slaughter.)