Carrier 38AUM Series, Installation, Operation & Maintenance Manual

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Table – CADM Troubleshooting
Miswired Module Indication Recommended Troubleshooting Action
Green LED is not on, module
does not power up
Determine if both R and C module terminals are connected. Verify voltage in present at module’s R
and C terminals.
NOTE: The CADM requires a constant nominal 24VAC power supply. The wiring to the module’s R
and C terminals must be directly from the control transformer. The module cannot receive its power from another
device that will interrupt the 24VAC power supply. See the 38AU Wiring Diagram(s) (Fig. 30 and Fig. 31).
Green LED Intermittent,
module powers up only
when compressor runs
Determine if R and Y terminals are wired in reverse. Verify module’s R and C terminals have a con- stant source.
See “
NOTE
” above for details on R and C wiring.
TRIP LED is on but system
and compressor check OK
Verify Y terminal is wired properly per the 38AU wiring diagram (see Fig. 30 and Fig. 31). Verify voltage at
contactor coil falls below 0.5VAC when off. Verify 24VAQC is present across Y and C when thermostat demand
signal is present. If not, R and C are reverse wired.
TRIP LED and ALERT LED
flashing together
Verify R and C terminals are supplied with 19-28VAC.
ALERT Flash Code 3
(Compressor Short Cycling)
displayed incorrectly
Verify Y terminal is connected to 24VAC at contactor coil. Verify voltage at contactor coil falls below
0.5VAC when off.
ALERT Flash Code 5 or 6 (Open
Circuit, Missing Phase)
displayed incorrectly
Check that compressor T1 and T3 wires are through module’s current sensing holes. Verify Y ter- minal is
connected to 24VAC at contactor coil. Verify voltage at contactor coil falls below 0.5VAC when off.
Alert Flash Code *
(Welded Contactor)
displayed incorrectly
Determine if module’s Y terminal is connected. Verify Y terminal is connected to 24VAC at contactor coil. Verify
24VAC is present across Y and C when thermostat demand signal is present. If not, R and C are reverse wired.
Verify voltage at contactor coil falls below 0.5VAC when off.
Compressor Protection
Compressor Overtemperature Protection (IP) — A thermostat installed on the compressor motor winding
reacts to excessively high winding temperatures and shuts off the compressor.
Crankcase Heater — The heater minimizes absorption of liquid refrigerant by oil in the crankcase during brief or
extended shutdown periods. The heater is wired to cycle with the compressor; the heater is off when compressor is
running, and on when compressor is off. The crankcase heater will operate as long as the power circuit is energized.
The main disconnect must be on to energize the crankcase heater.
Advanced Scroll Temperature Protection (ASTP) — See “Advanced Scroll Temperature Protection (ASTP)”
Low-Pressure Switch — The 38AUM low-pressure switch is stem-mounted on the suction line. Switches are all fixed,
non-adjustable type.
High--Pressure Switch — The high--pressure switch is stem mounted on the discharge line. The switch is a fixed,
non-adjustable type.
Outdoor Fans — Each fan is supported by a formed-wire mount bolted to the fan deck and covered with a wire guard.
Fan motors have permanently lubricated bearings.
1. Shut off unit power supply. Install lockout tag.
2. Remove outdoor fan assembly (grille, motor, and fan).
3. Loosen fan hub setscrews.
4. Adjust fan height.
5. Tighten setscrews to 84 in-lbs (949 N-cm).
6. Replace outdoor fan assembly.
Fig: - Outdoor Fan Blade Position
IMPORTANT:
Never open any switch or disconnect that energizes the crankcase heater unless
unit is being serviced or is to be shut down for a prolonged period. After a prolonged shutdown
on a service job, energize the crankcase heater for 24 hours before starting the compressor.
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