Tecumseh AH5540E Service Handbook Download

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SERVICE HANDBOOK

Checking for Continuity and Proper Resistance

If no ground fault has been detected using the procedures on pages 40-41, 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 4-2 to check single- and 3-phase motors.

Table 4-2: Checking for Proper Continuity and Resistance

Single Phase Compressors

3-Phase Compressors

Step One

Allow Thermal

Protector to Reset

When servicing single compressors
with internal thermal protectors, be sure
to allow time for the thermal protector
to reset prior to starting these electrical
wiring checks. For some compressors,
the internal thermal protector may take
as long as an hour to reset

When servicing 3-phase compressors
with  internal  thermal  protectors,  be
sure to allow time for the thermal pro-
tector  to  reset  prior  to  starting  these
electrical  wiring  checks.  For  some
compressors,  the  internal  thermal
protector may take as long as an hour
to reset

Step Two

Check Continuity

Check the start winding by measuring
continuity between terminal pins C and
S. (See "Identification of Terminal Pins"
on  page  26.  If  there  is  no  continuity,
replace  the  compressor.  See  "System
Cleanup  and  Compressor  Replace-
ment  After  Compressor  Failure"  on
pages 83-86.
Check  the  run  winding  by  measuring
continuity between terminal pins C and
R. If there is no continuity, replace the
compressor.

Check the windings by measuring be-
tween each pair of terminal pins: Leg1

- Leg2, Leg2 - Leg3, and Leg1 - Leg3.

If  there  is  no  continuity,  replace  the
compressor.  See  "System  Cleanup
and  Compressor  Replacement  After
Compressor Failure" on pages 83-86.

Step Three

Measure the

Resistance

Measure  the  resistance  (ohms)  be-
tween each pair of terminal pins: C and
S, C and R, and S and R. Add the resis-
tance between C and S to the resistance
between  C  and  R.  This  sum  should
equal the resistance found between S
and R. A small deviation in the compar-
ison  is  acceptable.  Proper  resistance
may  also  be  confirmed  by  comparing
measured resistance to the resistance
specifications for the specific compres-
sor  model.  Call  1-800-211-3427  to  re-
quest  resistance  specifications.  If  the
resistance  is  not  correct,  replace  the
compressor. See "System Cleanup and
Compressor  Replacement  After  Com-
pressor Failure" on pages 83-86. If the
resistance is correct, leave the leads off
and  follow  the  instructions  in  the  next
section  to  check  other  compressor
electrical components.

Measure the resistance (ohms) be-
tween each pair of terminal pins: Leg1

- Leg2, Leg2 - Leg3, and Leg1 - Leg3.

The resistance found between each
of the pairs Leg1 - Leg2, Leg2 - Leg3,

and Leg1 - Leg3 should all be greater

than  zero  and  within  approximately
10% of one another. Proper resistance
may also be confirmed by comparing
measured resistance to the resistance
specifications  for  the  specific  com-
pressor  model.  Call  1-800-211-3427
to  request  resistance  specifications.
If the resistance of Leg1 - Leg2, Leg2

- Leg3, and Leg1 - Leg3 does not

approximate  the  resistance  of  each
other, then there is a short circuit. Re-
place  the  compressor.  See  "System
Cleanup  and  Compressor  Replace-
ment  After  Compressor  Failure"  on
pages 83-86.