Component Testing; Compressor; Resistance Test; Ground Test - Maytag ATB1821AR series Service Manual

Component Testing

To avoid risk of electrical shock, personal injury, or death, disconnect electrical power source to unit, unless test
procedures require power to be connected. Discharge capacitor through a resistor before attempting to service.
Ensure all ground wires are connected before certifying unit as repaired and/or operational.
Component Description

Compressor

When compressor electrical circuit is
energized, the start winding current
causes relay to heat. After an amount of
starting time, the start winding circuit
turns off. The relay will switch off the start
winding circuit even though compressor
has not started (for example, when
attempting to restart after momentary
power interruption).
With "open" relay, compressor will not
start because there is little or no current
to start windings. Overload protection will
open due to high locked rotor run winding
current.
With "shorted" relay or capacitor,
compressor will start and overload
protector will quickly open due to high
current of combined run and start
windings.
With open or weak capacitor,
compressor will start and run as normal
but will consume more energy.
©2005 Maytag Services
!
WARNING
Test Procedures

Resistance test

1. Disconnect power to unit.
2. Discharge capacitor by shorting across terminals with a resistor for 1 minute.
NOTE: (Some compressors do not use a run capacitor.)
3. Remove leads from compressor terminals.
4. Set ohmmeter to lowest scale.
5. Check for resistance between
Terminals "S" and "C", start winding
Terminals "R" and "C", run winding
If either compressor winding reads open (infinite or very high resistance) or
dead short (0 ohms), replace compressor.

Ground test

1. Disconnect power to refrigerator.
2. Discharge capacitor, if present, by shorting terminals through a resistor.
3. Remove compressor leads and use an ohmmeter set on highest scale.
4. Touch one lead to compressor body (clean point of contact) and other probe
to each compressor terminal.
• If reading is obtained, compressor is grounded and must be replaced.

Operation test

If voltage, capacitor, overload, and motor winding tests do not show cause for
failure, perform the following test:
1. Disconnect power to refrigerator.
2. Discharge capacitor, if present, by shorting terminals through a resistor.
3. Remove leads from compressor terminals.
4. Wire a test cord to power switch.
5. Place time delayed fuse with UL rating equal to amp rating of motor in test
cord socket. (Refer to Technical Data Sheet)
6. Remove overload and relay.
7. Connect start, common and run leads of test cord on appropriate terminals of
compressor.
8. Attach capacitor leads of test cord together. If capacitor is used, attach
capacitor lead to a known good capacitor of same capacity.
9. Plug test cord into wattmeter to determine start and run wattage and use a
multimeter to check for low voltage, which can also be a cause of a
compressor not starting.
10. With power to multimeter, press start cord switch and release.
• If compressor motor starts and draws normal wattage, compressor is okay
and trouble is with either the capacitor, relay/overload, temperature
control, or elsewhere in system.
• If compressor does not start when direct wired, recover refrigerant at high
side. After refrigerant is recovered, repeat compressor direct wire test. If
compressor runs after recovery but would not run when direct wired
before recover, a restriction in sealed system is indicated.
• If compressor does not run when wired direct after recovery, replace faulty
compressor.
5
To AC supply
Switch
Compressor
Fuses
C S
R
Capacitor
Test configuration
16025860