Service Manual
Table Of Contents
16
f) Comp and ConFM Diagnosis: Conrm Comp and ConFM energize. Ifnot, check for
115VAC at CM 1 (C) (V) to a neutral(W). If 115VAC is not present, check CTh status.
See "II.D. Thermistor Check." IfCTh ohm reading is in proper range, replace CM.
If not in range, replace thermistor. If115VAC is present at CM 1 (C) (V) to a neutral
(W), check for 115VAC at both HPS (V) wires to a neutral(W). If 115VAC is present
on one and not the other, check HPS continuity. If open, allow time for HPS to reset.
If HPS does not reset, see "g) HPS Activation" below. If HPS is closed and 115VAC
present on both HPS (V) wires to a neutral (W), check for 115VAC at condensing unit
receptacle and condensing unit power supply cord (BK) to a neutral (W). If 115VAC
is not present at condensing unit receptacle or power supply cord (BK), correct loose
wiring or replace receptacle or 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 both Comp external protector wires to a neutral (W). If 115VAC is present
on one and not the other, external protector is open. Give external protector time 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 Comp
start capacitor, start relay, and Comp motor windings, replace as needed. 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) 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–MH continues. 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."
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.