Service Manual
Table Of Contents
20
f) Comp and ConFM Diagnosis: Conrm Comp and ConFM energize. Ifnot, check
for 115VAC at CM 1 (C) (V) to neutral(W). If 115VAC is not present, check CTh
status. See "II.D. Thermistor Check." IfCTh ohm reading is in proper range, and
115VAC is not present at CM 1 (C) (V) to neutral(W), replace CM. If thermistor ohm
reading is not in range, replace thermistor. If115VAC is present at CM 1 (C) (V) to
neutral (W), check for 115VAC at CUR (V) to neutral(W). If 115VAC is not present,
check continuity of HPS. If open, allow time for HPS to reset. If HPS does not reset,
see "h) HPS Activation" below. If HPS is closed and 115VAC present, check for
115VAC at condensing unit power supply cord (BK) to neutral (W).If 115VAC is not
present at condensing unit power supply cord (BK), replace condensing unit power
supply cord. If 115VAC is present at condensing unit power supply cord (BK) and
ConFM is energized but Comp is not, check for 115VAC at Comp external protector
to neutral (W). If 115VAC is not present, give time for external protector to cool and
reset. If Comp external protector does not reset, replace Comp external protector.
If 115VAC is present on both Comp external protector wires, check run capacitor
(2-Section), start capacitor, start relay, and Comp motor windings. If Comp does not
start, replace condensing unit. If ConFM is not energized, check ConFM fan blades
for binding and motor winding continuity.
If Comp and ConFM are energized and the cabinet does not cool down, check for a
restriction in the refrigeration circuit, correct TXV operation, and correct refrigerant
charge. See nameplate for correct charge amount.
g) EvapFM Diagnosis: Conrm that EvapFM(s) energizes 30-sec. after startup.
If not, conrm DTh is above 32°F (0°C). If above 32°F (0°C), wait for evaporator to
cool down. Next, conrm doors are closed and DS engaged, check DS continuity.
IfDS is engaged and contacts are open, replace DS. If DS is engaged and contacts
are closed, check for 115VAC at CM 5 (F) dark blue (DBU) wire to neutral white (W)
wire. If 115VAC is not present, replace CM. If 115VAC is present, check EvapFM
blades for binding and EvapFM continuity.
h) HPS Activation: Conrm ConFM is energized and fan blade turns freely.
Conrmcondenser coil is not clogged or restricted. Conrm there are no restrictions
in the refrigeration circuit (TXV and drier). Let refrigeration circuit pressures equalize.
IfHPS does not reset and pressures are equalized, replace HPS. Ifpressures are
not equalized, reclaim refrigerant and diagnose refrigeration circuit restriction.
6) Cool Down Achieved–PH, MH, and DrH continue. CTh cools to 3°F (1.7°C) below
setpoint. Comp icon turns off and Comp and ConFM de-energize. EvapFM icon
stays on and EvapFM continues. 60-sec. later, EvapFM icon turns off and EvapFM
de-energizes.
a) Diagnosis: Conrm Comp icon turns off and Comp and ConFM de-energize. Ifnot,
and Comp and ConFM were energized longer than 2 min., check CTh status.
See"II.D. Thermistor Check." Replace as needed.
b) CM, Comp, ConFM, and EvapFM Diagnosis: IfCTh ohm reading is in proper
range and Comp continues, check for 115VAC at CM 1 (C) (V) to neutral (W).
If115VAC is present at CM 1 (C) (V), replace CM. 1-min. after Comp icon turns off,
conrm EvapFM icon turns off and EvapFM de-energizes. If not, check for 115VAC
at CM 5 (F) (DBU) to neutral (W). If 115VAC is present, replace CM.