Emerson 750 No Cool, Heat, Cool or Fan Runs Constantly, Furnace Cycles Too Fast or Too Slow

8 TROUBLESHOOTING

Symptom	Possible Cause		Corrective Action
No Heat (continued)	5.	Heating system requires service or	Diagnostic: Set SYSTEM Switch to HEAT and
		raise thermostat requires replacement.	the setpoint above room temperature. Within a few
			seconds the thermostat should make a soft click
			sound. This sound usually indicates the thermo-
			stat is operating properly. If the thermostat does
			not click, try the reset operation listed above. If the
			thermostat does not click after being reset contact
			your heating and cooling service person or place
			of purchase for a replacement. If the thermostat
			clicks, contact the furnace manufacturer or a
			service person to verify the heating is operating
			correctly.
No Cool	1.	SYSTEM Switch not set to COOL.	Set SYSTEM Switch to COOL and lower setpoint
			temperature below room temperature.
	2. Loose connection to thermostat or system.		Verify thermostat and system wires are securely
			attached.
	3.	Cooling system requires service or	Same procedure as diagnostic for No Heat
		thermostat requires replacement.	condition except set the thermostat to COOL and
			lower the setpoint below the room temperature.
			There may be up to a five minute delay before the
			thermostat clicks in Cooling.
Heat, Cool or Fan Runs Constantly.	1.	Possible short in wiring.	Check each wire connection to verify they are not
	2.	Possible short in thermostat.	shorted or touching together. No bare wire should
	3.	Possible short in heat/cool/fan system.	stick out from under terminal screws. Try resetting
	4.	FAN Switch set to Fan ON.	the thermostat as described above. If the condition
			persists the manufacturer of your system or
			service person can instruct you on how to test the
			Heat/Cool system for correct operation. If the
			system operates correctly, replace the thermostat.
Furnace Cycles Too Fast or Too Slow	1.	The location of the thermostat and/or the	Digital thermostats normally provide precise
(narrow or wide temperature swing)		size of the Heating System may be	temperature control and may cycle faster than
		influencing the cycle rate.	some older mechanical models. A faster cycle
			rate means the unit turns on and off more
			frequently but runs for a shorter time so there is
			no increase in energy use. If you would like to
			increase the cycle time, clip Jumper W-905 as
			mentioned in the instructions for Hydronic Heating
			Systems. It is not possible to shorten the cycle
			time. If an acceptable cycle rate is not achieved as
			received or by clipping W-905 contact a local
			service person for additional suggestions.
Cooling Cycles Too Fast or Too Slow	1.	The location of the thermostat and the size	The cycle rate for cooling is fixed and can not be
(narrow or wide temperature swing)		of the Cooling System can influence the	adjusted. Contact a local service person for
		cycle rate.	suggestions.
Thermostat Setting and Thermostat	1.	Thermostat thermometer setting requires	The thermometer can be adjusted +/- 3 degrees.
Thermometer Disagree		adjustment.	See Temperature Display Adjustment in the
			Operation section.
Thermostat Does Not Follow Program	1.	AM or PM set incorrectly in program.	Check current clock and program settings
	2.	AM or PM set incorrectly on the clock.	including the AM or PM designations for each
	3.	Voltage spike or static discharge.	time period. If a voltage spike or a static discharge
			occurs use the Reset Operation listed above.
Blank Display and/or Keypad	1.	Voltage spike or static discharge.	Replace batteries and check heat/cool system
Not Responding	2.	Battery change required.	for proper operation. If a voltage spike occurs use
			the Reset Operation listed above.

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