S-17C Unloader Test Procedure; S-17D Operation Test - Daikin ComfortNet DX18TC Service Instructions Manual

SERVICING
1. DO NOT remove protective terminal cover. Disconnect
the three leads going to the compressor terminals at the
nearest point to the compressor.
2. Identify the leads and using an ohmmeter on the R x
10,000 scale or the highest resistance scale on your
ohmmeter check the resistance between each of the
three leads separately to ground (such as an unpainted
tube on the compressor).
3. If a ground is indicated, then carefully remove the
compressor terminal protective cover and inspect for
loose leads or insulation breaks in the lead wires.
4. If no visual problems indicated, carefully remove the leads
at the compressor terminals.
5. Carefully retest for ground, directly between compressor
terminals and ground.
6. If ground is indicated, replace the compressor. The
resistance reading should be infinity. If there is any
reading on meter, there is some continuity to ground and
compressor should be considered defective.
OHMMETER
WARNING
Damage can occur to the glass embedded terminals if
the leads are not properly removed. This can result in
terminal and hot oil discharging.

S-17C UNLOADER TEST PROCEDURE

Unloader Test Procedure with Comfort Alert™-Unitary
(UC) Control Diagnostics
If you suspected that the unloader is not working, the
following methods may be used to verify operation.
UNLOADER SOLENOID
(Molded Plug)
1. Operate the system and measure compressor amper-
age. Cycle the unloader on and off at ten second intervals
by appling and removing Y2 voltage to the module. Wait
five seconds after power is applied to Y2 before taking a
reading. An increase in compressor amperage should be
observed when switching from part-load to full-load and a
reduction in compressor amperage should be observed
when changing from full-load to part-load. The percent
change in current depends on the operating conditions
and voltage.
2. If Step 1 does not give the expected results remove the
solenoid plug from the compressor and with the unit
running and the thermostat calling for Y2 to be energized
test the voltage output at the plug with a dc voltmeter. The
reading should be 4 to 18 VDC for Comfort Alert. If not,
unplug the harness from the module and check voltage at
the "High" pins of the module. The module will not power
the unloader solenoid if the compressor is not running.
3. If the correct DC voltage is at the control circuit molded
plug measure the unloader coil resistance. Shut off power
and remove the control circuit molded plug from the
compressor and measure te unloader solenoid coil resis-
tance. If the coil resistance is infinite, zero, or grounded,
the compressor must be replaced.

S-17D OPERATION TEST

If the voltage, capacitor, overload and motor winding test fail
to show the cause for failure:
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
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