Carrier 33CS - Troubleshooting

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
PC 111 Catalog No. 533-384 Printed in U.S.A. Form 33CS-44SI Pg 8 105 8-01 Replaces: 33CS-13SI
Book 1 4
Tab 11a 13a
Copyright 2001 Carrier Corporation
TROUBLESHOOTING
PROBLEM SOLUTION
Display on thermostat not illuminated Check for 24 vac at the R terminal connection. Terminal R must be
connected for proper thermostat operation.
“Service Filter” is displayed on thermostat After the configured number of blower operating hours, the Service
Filter message will be displayed. This reminds the owner to replace
the filter. Reset the Service Filter feature to reset the blower operation
timer to 0 hours.
Cooling will not energize Select COOL mode. Decrease cooling set point to 10 degrees below room
temperature. Check for 24 vac at Y1 terminal with a load connected. If present,
thermostat is operating correctly and problem is with wiring or equipment. If
24 vac is not present, replace the thermostat. Check for Compressor Cycle per
Hour Limit. Cooling may be locked out.
Heating will not energize Select HEAT mode. Increase heating set point to 10 degrees above
room temperature. Check for 24 vac at W1/O/B terminal with a load connected.
If present, thermostat is operating correctly and problem is with wiring or equip-
ment. If 24 vac is not present, replace the thermostat.
When using 4 wires (R,G,W,Y), the cooling equip-
ment tries repeatedly to turn on, but cannot. At
times the display dims or disappears.
There is not enough power available. Connect a 270-ohm, 10-watt power
resistor at the air-conditioning equipment between terminals W and C
(non-heat pump applications only).
When using 4 wires (R,G,W,Y), the heating equip-
ment tries repeatedly to turn on, but cannot. At
times the display dims or disappears.
There is not enough power available. Connect a 270-ohm, 10-watt
power resistor at the air-conditioning equipment between terminals
Y and C (non-heat pump applications only).
When controlling a heat pump, heat comes on
during cooling cycle.
Configure thermostat for heat pump operation (Table 2, Step 3).
When calling for cooling, both heating and
cooling are energized.
The thermostat is configured for a heat pump. Configure the thermostat
for non-heat pump operation (Table 2, Step 3).
When controlling a commercial heat pump unit,
unit runs in reverse or heating is always on.
Commercial heat pumps require that Heat Pump Option on thermostat
is turned OFF.
The thermostat temperature displays rises to 99 F. There is not enough voltage to the thermostat. Check wiring and power supply.
The resistor labeled “L3” on the thermostat is burned
out and brown. Thermostat will not work.
The thermostat has been wired incorrectly and circuit board is burned out.
Thermostat must be replaced.
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