Honeywell T7200 - Troubleshooting

45 63-4038—7
M4416
SYMPTON POSSIBLE CAUSE ACTION
LCD TEMPERATURE
DISPLAY IS --°.
LCD IS BLANK.
Q7300 SWITCH 5 INCORRECTLY SET.
INCOMPLETE CIRCUIT. CHECK WIRING FOR SHORTS OR OPENS
BETWEEN THERMOSTAT AND REMOTE SENSOR.
CHECK POWER TO FURNACE OR AIR CONDITIONER.
• ON-OFF SWITCH
• FUSE OR CIRCUIT BREAKER
• LOOSE 24 VAC CONNECTION
—AT THERMOSTAT
—AT FURNACE/AIR CONDITIONER
• INCORRECT WIRING
—CHECK WIRING DIAGRAM
CHECK VOLTAGE AT SUBBASE.
• 20 TO 30 VOLTS BETWEEN PINS 1 AND 6 ON Q7300 9 PIN
CONNECTOR (SEE FIG. 34).
—REPLACE Q7300 IF NO VAC.
—REPLACE THERMOSTAT IF VAC PRESENT.
SYSTEM WITHOUT REMOTE SENSOR: CHECK THAT SWITCH 5
IS IN ON POSITION.
SYSTEM WITH REMOTE SENSOR: CHECK THAT SWITCH 5 IS
IN OFF POSITION.
•
•
NO ac VOLTAGE TO THERMOSTAT.
FAN DOES NOT RUN. Q7300 SWITCH 4 INCORRECTLY SET.
INOPERATIVE THERMOSTAT. CHECK FAN OPERATION:
• SET FAN SWITCH TO ON.
• SYSTEM SWITCH TO AUTO.
• PRESS 3 HOUR OCCUPIED KEY.
• WAIT AS LONG AS FIVE MINUTES AND FAN SHOULD START.
FAN STILL DOES NOT RUN:
• USE OHM METER TO CHECK FOR CONTINUITY BETWEEN RC
AND G ON THE SUBBASE.
—IF ZERO, PROBLEM IS IN HVAC UNIT CONTROL SYSTEM.
•• CHECK FAN CONTROL RELAY CIRCUITS.
—IF NOT ZERO, REPLACE THERMOSTAT.
SET SWITCH 4 TO ON WHEN THERMOSTAT IS NOT REQUIRED
TO TURN ON FAN IN HEATING.
SET SWITCH 4 TO OFF WHEN THERMOSTAT IS REQUIRED TO
TURN ON THE FAN IN HEATING.
•
•
FAN DOES NOT
STOP.
HVAC SYSTEM OR THERMOSTAT
PROBLEM.
ALL SEGMENTS OF
LCD ARE DISPLAYED.
THERMOSTAT IS IN TEST MODE.
PRESS CLOCK AND DAY KEYS AT THE SAME TIME. REPLACE
THERMOSTAT IF REPEATED ATTEMPTS FAIL.
BATT DISPLAYED ON
LOWER RIGHT LCD.
THERMOSTAT HAS DETECTED LOW
BATTERY VOLTAGE.
• CHECK BATTERY CONNECTIONS.
• REPLACE BATTERY.
LCD DISPLAYS ----.
THERMOSTAT HAS NO PROGRAM.
• CHECK BATTERY (7.5 VDC).
• CHECK BATTERY CONNECTIONS.
• REPROGRAM THERMOSTAT.
• CHECK OPERATION. IF BATTERY OK AND THERMOSTAT LOOSES
PROGRAM, REPLACE THERMOSTAT.
LCD HAS ONLY
PARTIAL DISPLAY.
FAULTY THERMOSTAT. REPLACE T7300.
REMOVE WIRE FROM G TERMINAL.
• IF FAN KEEPS RUNNING:
—CHECK HVAC CONTROL WIRING.
—CHECK FOR LATCHED FAN CONTACTOR, RELAY OR PLENUM
SWITCH.
• IF FAN STOPS RUNNING:
—PRESS CONT UNOC KEY.
—CHECK THAT ROOM TEMPERATURE IS BETWEEN UNOC
HEATING AND COOLING SETPOINTS.
—WAIT FIVE MINUTES.
•• IF FAN KEEPS RUNNING, REPLACE THERMOSTAT.
•• IF FAN STOPS RUNNING, THERMOSTAT AND HVAC
SYSTEM ARE OK.
Troubleshooting
Refer to Figs. 47 and 48 to troubleshoot problems with the thermostat and system.
Fig. 47—Troubleshooting chart to quickly isolate a display or fan problem.
T7200/T7300/Q7300
TROUBLESHOOTING